Section II. DICYRTIDA, Haeckel, 1862, Monogr. d. Radiol., pp. 280, 296.

Definition.—Cyrtoidea dithalamia, with two-jointed shell, being divided by a transverse collar stricture into an apical joint (or cephalis) and a basal joint (or thorax).

Synopsis of the three Families and six Subfamilies of Dicyrtida.

Family LXII. Tripocyrtida.

Three radial apophyses.

Mouth open,1. Sethopilida.
Mouth closed,2. Sethoperida.

Family LXIII. Anthocyrtida.

Numerous radial apophyses.

Mouth open,3. Sethophormida.
Mouth closed,4. Sethophænida.

Family LXIV. Sethocyrtida.

No radial apophyses.

Mouth open,5. Sethocorida.
Mouth closed,6. Sethocapsida.

Family LXII. Tripocyrtida.

Three radial apophyses.

Mouth open,
1. Sethopilida.
Mouth closed,
2. Sethoperida.

Family LXIII. Anthocyrtida.

Numerous radial apophyses.

Mouth open,
3. Sethophormida.
Mouth closed,
4. Sethophænida.

Family LXIV. Sethocyrtida.

No radial apophyses.

Mouth open,
5. Sethocorida.
Mouth closed,
6. Sethocapsida.

Family LXII. Tripocyrtida, n. fam.

Sethopilida et Sethoperida, Haeckel, 1881, Prodromus, pp. 431, 433.

Definition.—Dicyrtida triradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, and bearing three radial apophyses.)

The family Tripocyrtida, composed of the Sethopilida and Sethoperida of my Prodromus, comprises those Cyrtoidea in which the lattice-shell is two-jointed and bears three radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethopilida is a simple wide opening, but in the Sethoperida is closed by a lattice-plate; the former are here divided into sixteen, the latter into eight different genera. Though probably the two shell-joints are not truly homologous in all Tripocyrtida, we call the first joint here, as in all Dicyrtida, the cephalis, and the second joint the thorax.

Numerous Tripocyrtida, living as well as fossil forms, were formerly described by Ehrenberg. His genera Dictyophimus, Clathrocanium, Lithomelissa, and Lychnocanium belong to the Sethopilida, and have the mouth open; his genera Lithopera and Lithochytris (partly) belong to the Sethoperida, and have the basal mouth closed by a lattice-plate. Many of these Tripocyrtida belong probably to the oldest forms of Dicyrtida, are nearly related to the Phormospyrida, and therefore of special phylogenetic interest, as was demonstrated by Bütschli (1882, loc. cit., pp. 514-519). This near relation to certain Spyroidea (Tripospyris, Acrospyris, &c.) is particularly striking in some forms of Clathrocanium, Lithomelissa, &c. Some other Tripocyrtida seem to possess a closer relation to certain Plectoidea (Plagoniscus, Plectaniscus), so mainly some forms of Tripocyrtis and Dictyophimus.

The cephalis, or the first joint of the shell, corresponds usually to the whole shell of the Zygospyrida and of numerous Monocyrtida, and exhibits various modifications of shape, which have been already described in these latter families. It is usually subspherical or hemispherical and armed with an apical horn. In a small number of genera the horn is lost, in some other genera multiplied. The cephalis is separated from the thorax not only externally by the collar constriction, but commonly also internally by a transverse horizontal fenestrated septum, which usually exhibits three or four characteristic cortinar pores. The central capsule, originally enclosed in the cephalis, develops usually three or four large pear-shaped cæcal sacs which pass through the cortinar pores and depend into the thorax (Pl. [55], figs. 2-11; Pl. [60], figs. 3-7, &c.).

The thorax in this family exhibits a great variety of interesting modifications, mainly in the development of the three radial apophyses arising from it. These may be either enclosed in the wall of the thorax as ribs, or arise as free wings, very often prolonged over the mouth as three terminal feet. Finally the three terminal feet only remain, whilst the original ribs are lost. The special ornamentation of these three apophyses exhibits an extraordinary variety and elegancy of structure, and many Tripocyrtida belong, no doubt, to the most graceful and admirable forms of Nassellaria.

Synopsis of the Genera of Tripocyrtida.

I. Subfamily Sethopilida.

Terminal mouth of the thorax a simple wide opening.

A. Three radial ribs (or cortinar rods) partly or completely enclosed in the wall of the thorax. No latticed vertical cephalic wings.a. Three thoracic ribs prolonged into three terminal feet.Cephalis with a horn.Feet solid,534. Dictyophimus.
Feet latticed,535. Tripocyrtis.
No horn, feet solid,536. Sethopilium.
b. Three thoracic ribs prolonged into three lateral wings.Thorax perfectly latticed.With horn,537. Lithomelissa.
No horn,538. Psilomelissa.
Thorax with spongy framework,539. Spongomelissa.
Thorax with three large lateral holes between the three ribs,540. Clathrocanium.
c. Three thoracic ribs completely enclosed in the wall of the flat thoraxPeristome simple, smooth,541. Lamprodiscus.
Peristome with a corona of spines,542. Lampromitra.
B. Three radial ribs enclosed in the wall of the thorax and connected with the cephalic horn by three latticed vertical wings.a. Thorax completely latticedNo frontal horn (four spines),543. Callimitra.
With frontal horn (five spines),544. Clathromitra.
b. Thorax with three large lateral holes between the three ribs. No frontal horn,545. Clathrocorys.
C. Three radial beams (or cortinar rods) perfectly free, not enclosed in the wall of the thorax.Three beams outside the thorax, arising freely from the collar stricture (no cephalic hole),546. Eucecryphalus.
Three beams inside the thorax. Cephalis with a large apical hole,547. Amphiplecta.
D. Three radial terminal feet on the peristome (the three original lateral ribs are lost).Feet solid,548. Lychnocanium.
Feet latticed,549. Lychnodictyum.

II. Subfamily Sethoperida.

Terminal mouth of the thorax closed by a lattice-plate.

Three divergent ribs (or cortinar rods) enclosed either in the wall or in the cavity of the thorax.Three ribs enclosed in the lattice-wall of the thorax,550. Sethopera.
Three internal rods in the cavity of the thorax,551. Lithopera.
Three divergent free lateral wings (as prolongation of the three ribs) on the sides of the thorax.Three solid lateral spines.Cephalis with horn,552. Micromelissa.
No horn,553. Peromelissa.
Three latticed lateral wings. With horn,554. Sethomelissa.
Three free terminal feet (on the base of the thorax).Three feet solid,555. Tetrahedrina.
Three feet latticed.Shell without external mantle,556. Sethochytris.
Shell with an arachnoidal mantle,557. Clathrolychnus.
I. Subfamily Sethopilida. Terminal mouth of the thorax a simple wide opening.
A. Three radial ribs (or cortinar rods) partly or completely enclosed in the wall of the thorax. No latticed vertical cephalic wings.
a. Three thoracic ribs prolonged into three terminal feet.
Cephalis with a horn.
Feet solid,
534. Dictyophimus.
Feet latticed,
535. Tripocyrtis.
No horn, feet solid,
536. Sethopilium.
b. Three thoracic ribs prolonged into three lateral wings.
Thorax perfectly latticed.
With horn,
537. Lithomelissa.
No horn,
538. Psilomelissa.
Thorax with spongy framework,
539. Spongomelissa.
Thorax with three large lateral holes between the three ribs,
540. Clathrocanium.
c. Three thoracic ribs completely enclosed in the wall of the flat thorax
Peristome simple, smooth,
541. Lamprodiscus.
Peristome with a corona of spines,
542. Lampromitra.
B. Three radial ribs enclosed in the wall of the thorax and connected with the cephalic horn by three latticed vertical wings.
a. Thorax completely latticed
No frontal horn (four spines),
543. Callimitra.
With frontal horn (five spines),
544. Clathromitra.
b. Thorax with three large lateral holes between the three ribs. No frontal horn,
545. Clathrocorys.
C. Three radial beams (or cortinar rods) perfectly free, not enclosed in the wall of the thorax.
Three beams outside the thorax, arising freely from the collar stricture (no cephalic hole),
546. Eucecryphalus.
Three beams inside the thorax. Cephalis with a large apical hole,
547. Amphiplecta.
D. Three radial terminal feet on the peristome (the three original lateral ribs are lost).
Feet solid,
548. Lychnocanium.
Feet latticed,
549. Lychnodictyum.
II. Subfamily Sethoperida. Terminal mouth of the thorax closed by a lattice-plate.
Three divergent ribs (or cortinar rods) enclosed either in the wall or in the cavity of the thorax.
Three ribs enclosed in the lattice-wall of the thorax,
550. Sethopera.
Three internal rods in the cavity of the thorax,
551. Lithopera.
Three divergent free lateral wings (as prolongation of the three ribs) on the sides of the thorax.
Three solid lateral spines.
Cephalis with horn,
552. Micromelissa.
No horn,
553. Peromelissa.
Three latticed lateral wings. With horn,
554. Sethomelissa.
Three free terminal feet (on the base of the thorax).
Three feet solid,
555. Tetrahedrina.
Three feet latticed.
Shell without external mantle,
556. Sethochytris.
Shell with an arachnoidal mantle,
557. Clathrolychnus.

Subfamily 1. Sethopilida, Haeckel, 1881, Prodromus, p. 431.

Definition.—Tripocyrtida, with the basal mouth of the shell open (vel Dicyrtida triradiata aperta).

Genus 534. Dictyophimus,[[151]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 53.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three complete thoracic ribs, prolonged into three solid divergent feet on the peristome. Cephalis with an apical horn.

The genus Dictyophimus, comprising many common species, may be regarded as the common ancestral form of all sethopilida, and therefore also of the whole family of Dicyrtida. The cephalis bears an apical horn, and the thorax three ribs, which are prolonged over the open mouth into three solid feet. Dictyophimus may be derived either from Euscenium or Peridium (Archiperida), or from Tripospyris (Zygospyrida), or from Plectaniscus (Plectanida), by development of lattice-work between the three terminal feet, which therefore become thoracic ribs.

Subgenus 1. Dictyophimium, Haeckel.

Definition.—Shell smooth or rough, without prominent spines on the edges of the three thoracic ribs. (Commonly one single horn on the cephalis.)

1. Dictyophimus sphærocephalus, n. sp. (Pl. [57], fig. 10).

Shell smooth, with a deep collar stricture, separating two joints of nearly equal size. Cephalis subglobular, rough, with a stout pyramidal horn of half the length, and regular, circular, hexagonally framed pores. Thorax nearly three-sided prismatic, smooth, with three stout, little divergent or nearly parallel ribs, which are prolonged into conical subvertical feet half as long. Thoracic pores irregular, roundish.

Dimensions.—Cephalis 0.08 long, 0.08 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Dictyophimus tripus, Haeckel.

Dictyophimus tripus, Haeckel, 1862, Monogr. d. Radiol., p. 306, Taf. vi. fig. 1.

Shell with a slight collar stricture, separating two joints of slightly different size. Cephalis nearly ellipsoidal, large, with a slender conical horn of the same length. Thorax truncate three-sided pyramidal, with three strongly divergent ribs, which are prolonged into three slender conical feet of about the same length. Pores irregular, roundish, of variable size.

Dimensions.—Cephalis 0.032 long, 0.028 broad; thorax 0.34 long, 0.064 broad.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands), surface.

3. Dictyophimus plectaniscus, n. sp. (Pl. [61], figs. 8, 9).

Shell flat, pyramidal, smooth, with distinct collar stricture. Cephalis hemispherical, with a conical horn of the same length and numerous small regular pores. Thorax flat, triangular, pyramidal, with three widely divergent ribs, which are prolonged into three cylindrical feet of the same length. Thoracic pores fifteen, very large, subregular, roundish, disposed in two transverse girdles, the inner with six, the outer with nine pores; five pores between every two ribs.

Dimensions.—Cephalis 0.04 long, 0.06 broad; thorax 0.08 long, 0.18 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

4. Dictyophimus craticula, Ehrenberg.

Dictyophimus craticula, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. v. figs. 4, 5.

Dictyophimus craticula, Bütschli, 1882, Zeitschr. f. Wiss. Zool., vol. xxxvi. p. 515, Taf. xxxiii. fig. 35.

Shell flat, pyramidal, very similar to the preceding species, but differing in the rudimentary horn, which is smaller than half the cephalis, and in the length of the three cylindrical feet, which are twice to three times as long as the shell. The nine inferior large pores of the thorax are twice to three times as large as the six superior pores. The basal peristome is commonly thorny.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.1 long, 0.2 broad.

Habitat.—Fossil in Barbados.

5. Dictyophimus pyramis, n. sp. (Pl. [61], fig. 16).

Shell regular, pyramidal, with flat collar stricture. Relative length of the two joints = 1 : 4, breadth = 2 : 6. Cephalis hemispherical, with a stout pyramidal horn of the same length. Thorax triangular pyramidal, with three prominent ribs, which are prolonged into three slender pyramidal feet, half as long. Pores small and very numerous, subregular, circular.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.1 long, 0.15 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

6. Dictyophimus challengeri, Haeckel.

Dictyophimus challengeri, Haeckel, 1878, Protistenreich, p. 47, fig. 35.

Shell campanulate, with sharp collar stricture. Relative length of the joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a stout pyramidal horn of twice the length, and numerous very small pores. Thorax nearly hemispherical, with three vaulted bosoms between the three decurrent ribs, which are prolonged into three nearly parallel and vertical feet of about the same length. Pores subregular, circular, of medium size. This species is very similar to Lychnodictyum challengeri, Haeckel, but differs in the smaller straight horn and the longer solid feet, which are not fenestrated.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.13 broad.

Habitat.—Tropical Atlantic, Station 347, surface.

7. Dictyophimus lasanum, n. sp. (Pl. [61], fig. 5).

Shell nearly pear-shaped, with distinct collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis hemispherical, with a conical horn of the same length. Thorax nearly spherical, on both poles truncate and constricted, with three decurrent curved ribs and small regular circular pores. The prolongations of the ribs form three divergent pyramidal straight feet, nearly as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.09 long, 0.09 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

8. Dictyophimus longipes, n. sp. (Pl. [61], fig. 3).

Shell three-sided pyramidal, with distinct collar stricture. Relative length of the two joints = 1 : 4, breadth = 2 : 6. Cephalis hemispherical, with a rudimentary pyramidal horn, scarcely one-fourth as long; and with small circular regular pores. Thorax with larger irregular pores, and three vaulted bosoms between the three decurrent ribs, which are prolonged into three very long and slender prismatic feet, S-shaped, curved, and twice to three times as long as the shell.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.09 long, 0.13 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

9. Dictyophimus gracilipes, Bailey.

Dictyophimus gracilipes, Bailey, 1856, Amer. Journ. Sci. and Arts, vol. xxii. p. 4, pl. i. fig. 8.

Shell three-sided pyramidal, with a deep collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis hemispherical, with a thin horn of the same length. Thorax with three curved ribs, which are prolonged into three divergent angular feet of the same length. Pores irregular roundish.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.05 long, 0.08 broad.

Habitat.—North Pacific, Station 240, surface, Kamtschatka (Bailey).

10. Dictyophimus cortina, n. sp. (Pl. [61], fig. 1).

Shell three-sided pyramidal, with distinct collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a pyramidal horn of half the length. Thorax with much larger irregular roundish pores and three prominent ribs, which are prolonged into three stout, club-shaped, strongly divergent feet of the same length. Mouth widely open, elegantly coronate, with a circle of numerous small cilia.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

11. Dictyophimus arabicus, Haeckel.

Lychnocanium arabicum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 296, Taf. x. fig. 3.

Shell smooth, three-sided pyramidal, with deep collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a slender horn of the same length. Thorax with much larger, irregular roundish pores, and three widely divergent ribs, which are prolonged into three slender, somewhat recurved feet of about the same length.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Indian Ocean, Zanzibar (Pullen), depth 2200 fathoms.

12. Dictyophimus platycephalus, n. sp. (Pl. [60], figs. 4, 5).

Shell smooth, flat, three-sided pyramidal, with distinct collar stricture. Relative length of the two joints = 1 : 3, breadth = 3 : 9. Cephalis flat, cap-shaped, three times as broad as long, with a slender conical horn of the same length. Thorax flatly vaulted, with much larger, irregular roundish, double-edged pores, and three widely divergent ribs, which are prolonged into three slender conical feet of the same length. Central capsule in the cephalis flat, discoidal, with a discoidal nucleus of half the size, and with four large pear-shaped cæcal sacs depending into the thorax, each of which contains a large oil globule (fig. 4).

Dimensions.—Cephalis 0.02 long, 0.07 broad; thorax 0.06 long, 0.18 broad.

Habitat.—North Atlantic, Canary Islands (Lanzerote), Haeckel, surface.

13. Dictyophimus brandtii, n. sp. (Pl. [60], fig. 6).

Shell smooth, flat, three-sided pyramidal, with deep collar stricture, very similar to the preceding species. Relative length of the two joints = 1 : 3, breadth = 2 : 7. Cephalis hemispherical, with a slender conical horn of twice the length. Thorax flatly vaulted, with irregular polygonal pores and thin bars; and with three widely divergent ribs, which are prolonged into three slender prismatic feet of thrice the length. In fig. 6 the shell is seen from the base and exhibits very distinctly the collar septum with its four large meshes, two minor jugular and two major cardinal pores.

Dimensions.—Cephalis 0.03 long, 0.07 broad; thorax 0.08 long, 0.2 broad.

Habitat.—North Pacific, Station 236, surface.

14. Dictyophimus lucerna, Haeckel.

Lychnocanium lucerna, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 6; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 80, Taf. viii. fig. 3.

Lychnocanium lucerna, Haeckel, 1862, Monogr. d. Radiol., p. 311.

Shell smooth, three-sided pyramidal, with slight collar stricture. Relative length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis hemispherical, with a thick conical horn of twice the length. Thorax with small regular, circular pores and three flat sides; between these arise three rounded ribs, which are prolonged into three short, conical, divergent feet, one-third as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Fossil in Barbados.

15. Dictyophimus hamosus, Haeckel.

Lychnocanium hamosum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 9.

Shell pear-shaped, rough, with deep collar stricture. Relative length of the two joints = 1 : 2, breadth = 1 : 3. Cephalis subglobular, with a conical horn of twice the length. Thorax with small, regular, circular pores, and with three prominent ribs, prolonged into three vertical prismatic feet, which are about as long as the shell, parallel or a little convergent towards the distal end, with recurved teeth or hooks at the lateral edges.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Fossil in Barbados.

16. Dictyophimus tridentatus, Haeckel.

Lychnocanium tridentatum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 4.

Shell smooth, three-sided pyramidal, with deep collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a conical horn of the same length, and some small accessory thorns. Thorax tetrahedral, with three smooth hyaline walls, bearing only a single series of small pores on each side of the three prominent ribs, which are prolonged into three strong prismatic curved feet of twice the length, with the convexity external. A group of small pores and a strong triangular tooth at the base of each foot.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Lamprotripus, Haeckel, 1881, Prodromus, p. 432.

Definition.—Shell spiny or thorny, with prominent spines on the edges of the three thoracic ribs. (Commonly one larger and a few smaller horns or spines on the cephalis.)

17. Dictyophimus triserratus, n. sp. (Pl. [61], fig. 17).

Shell three-sided pyramidal, with slight collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis small, subspherical, with a large pyramidal horn three times as long. Thorax with much larger, irregular roundish, double-edged pores, and three prominent, serrate ribs, which are prolonged into three pyramidal strongly divergent feet of the same length.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.09 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

18. Dictyophimus bicornis, n. sp.

Shell thorny, with deep collar stricture. Relative length of the two joints = 2 : 3, breadth = 2 : 3. Cephalis nearly as large as the thorax, subglobular, with numerous small, circular pores, and two divergent pyramidal horns of half the length (a major occipital and a minor frontal horn). Thorax three-sided pyramidal, with larger irregular pores and three serrate ribs, which are prolonged into three prismatic spiny feet of half the length. (Differs from the similar Dictyophimus sphærocephalus, Pl. [57], fig. 10, mainly in the double horn and the spinulate feet.)

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.08 long, 0.07 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

19. Dictyophimus pocillum, Ehrenberg.

Dictyophimus pocillum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. v. fig. 6.

Shell thorny, with distinct collar stricture. Relative length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis nearly spherical, with numerous small conical spines. Thorax flat, three-sided pyramidal with large, irregular, roundish pores, and three strong, widely divergent, spinulate ribs, which are prolonged into three prismatic spinulate feet of the same length.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.15 long, 0.15 broad.

Habitat.—Fossil in Barbados.

20. Dictyophimus cienkowskii, n. sp. (Pl. [60], fig. 1).

Lamprotripus squarrosus, Haeckel, 1881, Prodromus et Atlas.

Shell spiny, flatly pyramidal, with slight collar stricture. Relative length of the two joints = 1 : 3, breadth = 2 : 6. Cephalis flat, cap-shaped, three times as long as broad, with numerous bristle-shaped spines three times as long. Thorax also spiny, with irregular, very large, polygonal meshes and thin bars; its three ribs prolonged into three very long and thin, widely divergent, prismatic feet, bearing numerous long spines on the three edges.

Dimensions.—Cephalis 0.025 long, 0.05 broad; thorax 0.075 long, 0.15 broad.

Habitat.—North Pacific, Station 250, surface.

21. Dictyophimus bütschlii, n. sp. (Pl. [60], fig. 2).

Lamprotripus horridus, Haeckel, 1881, Prodromus et Atlas.

Shell spiny, flatly pyramidal, with deep collar stricture. Relative length at the two joints = 1 : 2, breadth = 1 : 5. Cephalis subspherical, with numerous long, bristle-shaped spines and a larger ramified horn. Thorax also spiny, flatly vaulted, with large, subregular, hexagonal meshes and thin bars; its three spiny ribs prolonged into three very long and thin, prismatic, widely divergent feet, twice to four times as long as the thorax.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

Habitat.—South Pacific, Station 284, surface.

22. Dictyophimus hertwigii, n. sp. (Pl. [60], fig. 3).

Lamprotripus spinosus, Haeckel, 1881, Prodromus et Atlas.

Shell spiny, flatly pyramidal with sharp collar stricture. Relative length of the two joints = 1 : 2, breath = 1 : 5. Cephalis subspherical, with irregular roundish pores, numerous small spines and a large, oblique, prismatic horn of the same length, bearing on its distal end a bunch of small divergent spines. Thorax pyramidal, with larger irregular polygonal pores and thin bars; its three strong, widely divergent ribs spiny, straight, and prolonged into three prismatic slender feet of the same length. Central capsule with three lobes depending into the thorax.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

Habitat.—Central Pacific, Stations 270 to 274, surface.

Genus 535. Tripocyrtis,[[152]] n. gen.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three complete thoracic ribs, prolonged into three latticed divergent feet on the peristome. Cephalis with an apical horn.

The genus Tripocyrtis has been derived from the preceding Dictyophimus by complete fenestration of the three basal feet, which throughout their whole length become united by complete lattice-work. This genus is closely allied to Plectaniscus.

1. Tripocyrtis plagoniscus, n. sp. (Pl. [60], fig. 10).

Cephalis subspherical, with large, roundish meshes and a stout, three-sided pyramidal, irregularly branched horn of twice the length. Thorax with a small number of large, irregular, polygonal meshes and three stout curved ribs about as long as the cephalic horn.

Dimensions.—Cephalis 0.06 long, 0.07 broad; thorax 0.11 long, 0.16 broad.

Habitat.—Central Pacific, Station 266, surface.

2. Tripocyrtis tripodiscus, n. sp.

Cephalis subspherical, with small, polygonal pores and a large, arborescent, vertical horn of thrice the length, bearing numerous ramified branches. Thorax with three straight, widely divergent ribs, of the same length as the horn, connected by a delicate, arachnoidal framework with irregular, polygonal meshes.

Dimensions.—Cephalis 0.04 long, 05 broad; thorax 0.12 long, 0.18 broad.

Habitat.—Central Pacific, Station 269, surface.

3. Tripocyrtis plectaniscus, n. sp. (Pl. [60], fig. 9).

Cephalis subspherical, with small roundish pores, and a stout, three-sided pyramidal, denticulate horn of the same length. Thorax with three little divergent and curved ribs, twice as long as the horn, in the upper half with smaller, in the lower half with larger, polygonal, irregular meshes.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Central Pacific, Station 264, surface.

Genus 536. Sethopilium,[[153]] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three complete thoracic ribs, which are prolonged into three solid divergent feet on the peristome. Cephalis smooth, without a horn.

The genus Sethopilium differs from its probable ancestral form Dictyophimus by the complete loss of the cephalic horn, and of the collar septum between both joints, which are only separated by the slight external collar stricture.

1. Sethopilium orthopus, n. sp. (Pl. [97], fig. 8).

Shell smooth, with sharp collar stricture, Relative length of the two joints = 5 : 4, breadth = 7 : 6. Cephalis large, subspherical, with numerous regular circular pores, twice as broad as the bars. Thorax with three stout, straight, widely divergent ribs, prolonged into three straight pointed feet of the same length. Between every two ribs, in the centre of the collar stricture, a single large triangular mesh, and beyond this three to six rows of smaller irregular meshes.

Dimensions.—Cephalis 0.05 long, 0.07 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Sethopilium cyrtopus, n. sp.

Shell smooth, with sharp collar stricture. Relative length of the two joints = 4 : 6, breadth = 7 : 11. Cephalis hemispherical, with large irregular roundish pores, four times as broad as the bars. Thorax with three stout, curved, widely divergent ribs, prolonged into three cylindro-conical, curved feet of twice the length, which are convex in the proximal half, concave in the distal half. Between every two ribs, beyond the collar stricture, two large ovate meshes, and beyond this two rows of smaller irregular meshes.

Dimensions.—Cephalis 0.04 long, 0.07 broad; thorax 0.05 long, 0.11 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

3. Sethopilium macropus, n. sp. (Pl. [97], fig. 9).

Shell smooth, with slight collar stricture. Relative length of the two joints = 4 : 7, breadth = 6 : 13. Cephalis hemispherical, with irregular double-contoured pores, about as broad as the bars. Thorax with three very stout, carved, widely divergent ribs, prolonged into three curved, cylindrical, very long feet, which are three to four times as long as the shell, and convex on the outside. Between every two ribs, beyond the collar stricture, two large broad meshes, and beyond this two or three rows of smaller meshes.

Dimensions.—Cephalis 0.04 long, 0.06 broad; thorax 0.07 long, 0.13 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 537. Lithomelissa,[[154]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three free lateral wings, or solid spines arising from the sides of the thorax. No terminal feet. Cephalis with one or more horns.

The genus Lithomelissa, containing numerous and widely distributed forms, may like Dictyophimus be regarded as one of the most primitive and ancient forms of Dicyrtida. It differs from the latter by the lateral (not terminal) position of the three thoracic feet, and may be derived either from Dictyophimus (by secondary development of intrapedal network towards the mouth, on the inside of the three feet) or directly from Tripospyris by similar formation of thoracic network beyond the collar stricture, outside the base of the three divergent feet and pierced by the latter. As the species of this genus are numerous, it may perhaps be better to divide it into two or three genera: Acromelissa, with a single horn, Micromelissa, with two horns, and Sethomelissa, with three or more horns.

Subgenus 1. Acromelissa, Haeckel, 1881, Prodromus, p. 431.

Definition.—Cephalis with a single occipital horn.

1. Lithomelissa macroptera, Ehrenberg.

Lithomelissa macroptera, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. figs. 9, 10.

Shell smooth, with distinct collar stricture. Relative length of the two joints = 4 : 5, breadth = 3 : 4. Cephalis ovate, with a stout, excentric, vertical, pyramidal horn of the same length. Thorax little larger, ovate, truncate. Both joints with very small and scattered pores. Three divergent ribs arise from the base of the cephalic horn, and are prolonged over the major part of the thorax; their under free part arises from the middle part of the thorax and is as long as the horn, straight, pyramidal. Mouth truncate, little constricted.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.05 long, 0.04 broad.

Habitat.—Fossil in Barbados.

2. Lithomelissa ehrenbergii, Bütschli.

Lithomelissa ehrenbergii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 517, Taf. xxxiii. fig. 21a, b.

Lithomelissa macroptera, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 8.

(?) Lophophæna capito, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 6.

(?) Lophophæna galeata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 12.

Shell rough, with distinct collar stricture. Relative length of the two joints = 4 : 2, breadth = 3 : 4. Cephalis ovate, with a stout excentric, oblique, pyramidal horn of half the length. Thorax little shorter, truncate, conical. Both joints with regular circular pores, of the same breadth as the bars. Three divergent conical feet, as long as the cephalis, arise below the collar stricture. Mouth truncate, not constricted.

Dimensions.—Cephalis 0.08 long, 0.06 broad; thorax 0.04 long, 0.08 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; fossil in Barbados.

3. Lithomelissa macroceras, n. sp.

Shell spiny, with sharp collar stricture. Relative length of the two joints = 5 : 7, breadth = 5 : 6. Cephalis spherical, with a large pyramidal horn of twice the length. Thorax little longer, ovate, truncate. Both joints with regular circular pores, three times as broad as the bars. Three divergent pyramidal feet, twice as long as the cephalis, arise from the middle part of the thorax. Mouth constricted, half as broad as the thorax.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.07 long, 0.06 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

4. Lithomelissa mitra, Bütschli.

Lithomelissa mitra, Bütschli, 1881, Zeitschr. f. wiss. Zool., p. 518, Taf. xxxiii. fig. 24.

Shell smooth, with distinct collar stricture. Relative length of the two joints = 5 : 4, breadth = 4 : 5. Cephalis ovate, with a slender, straight, vertical, pyramidal horn of the same length. Thorax ovate, truncate, of about the same size. Both joints with very small and numerous pores, as broad as the bars. Three feet arising from the middle part of the thorax, very small, rudimentary, pyramidal, about as long as broad. Mouth truncate, little constricted.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.04 long, 0.05 broad.

Habitat.—Fossil in Barbados.

5. Lithomelissa pycnoptera, n. sp.

Shell rough, papillate, with slight collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis small, hemispherical, with very small pores and a slender, straight, conical horn of twice the length. Thorax subconical, with regular circular, hexagonally framed pores, as broad as the bars. From its lower half arise three divergent, very strong feet, pyramidal, as long as the thorax, and three times as long as broad.

Dimensions.—Cephalis 0.03 diameter, thorax 0.1 diameter.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

6. Lithomelissa microstoma, n. sp.

Shell papillate, with slight collar stricture. Relative length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis small, hemispherical, with a conical horn of twice the length. Thorax subspherical, with subregular circular pores, three times as broad as the bars. From its middle part arise three divergent, stout, conical feet, of half the length, and twice as long as broad. Mouth small, strongly constricted, one-fourth to one-third as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.15 diameter.

Habitat.—Fossil in Barbados.

7. Lithomelissa amphora, Stöhr.

Lithomelissa amphora, Stöhr, 1880, Palæontograph, vol. xxvi. p. 100, Taf. iii. fig. 11.

Shell smooth, with sharp collar stricture. Relative length of the two joints = 1 : 5, breadth = 2 : 4. Cephalis small, hemispherical, with a cervical horn of the same length. Thorax ovate, with small regular circular pores, twice as broad as the bars. From its upper half arise three divergent, slender, conical feet, only one-fourth as long. Mouth constricted, with a hyaline peristome, half as broad as the thorax.

Dimensions.—Cephalis 0.013 long, 0.026 broad; thorax 0.063 long, 0.053 broad.

Habitat.—Fossil in tertiary rocks of Sicily; Grotte (Stöhr).

Subgenus 2. Micromelissa, Haeckel, 1881, Prodromus, p. 433 (sensu emendato).

Definition.—Cephalis with two divergent horns, a superior occipital horn and an inferior frontal horn.

8. Lithomelissa thoracites, Haeckel.

Lithomelissa thoracites, Haeckel, 1862, Monogr. d. Radiol., p. 301, Taf. vi. figs. 2-8.

Lithomelissa thoracites, R. Hertwig, 1879, Organism. d. Radiol., p. 76, Taf. viii. fig. 1.

Shell smooth, with deep collar stricture. Cephalis ovate, with two divergent, slender, conical horns, of about half the length; a major oblique occipital horn on the posterior face, and a minor, nearly horizontal horn above the collar stricture, on the anterior face. Thorax about as large as the cephalis, truncate, ovate. Pores of both joints irregular, roundish, of different sizes. From the upper half of the thorax, below the collar stricture, there arise three slender, conical divergent feet, about as long as the cephalis. Mouth truncate, wide open, not constricted. On the numerous varieties of this common species compare my Monograph, on the structure of the ovate central capsule (enclosed in the cephalis), Hertwig, loc. cit.

Dimensions.—Cephalis 0.05 to 0.08 long, 0.04 broad; thorax 0.03 to 0.05 long, 0.05 to 0.07 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

9. Lithomelissa mediterranea, J. Müller.

Lithomelissa mediterranea, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 45, Taf. vi. fig. 11.

Lithomelissa mediterranea, Haeckel, 1862, Monogr. d. Radiol., p. 302.

Shell smooth, with sharp collar stricture. Relative length of the two joints = 4 : 5, breadth = 4 : 5. Cephalis campanulate, conical, with two divergent small conical horns, a major occipital subvertical horn near the summit, and a minor sub-horizontal frontal horn near the collar stricture. Thorax truncate, ovate, little larger than the cephalis. From its lower part there arise three short conical, divergent feet, scarcely half as long as the cephalis (in Müller's figure one of them is seen shortened, opposite to the frontal horn). Pores irregular, roundish, much smaller in the cephalis than in the thorax. Mouth wide open, not constricted.

Dimensions.—Cephalis 0.04 diameter, thorax 0.05 diameter.

Habitat.—Mediterranean (French shore), J. Müller, surface.

10. Lithomelissa bicornis, Ehrenberg.

Lithomelissa bicornis, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. ii. fig. 7.

Shell smooth, with deep collar stricture. Relative length of the two joints = 1 : 3, breadth = 1 : 2. Cephalis hemispherical, with two divergent, stout and straight, pyramidal horns; a larger occipital horn sub-vertical near the summit, and a smaller oblique frontal horn near the collar stricture. Thorax subspherical, twice as large, with larger irregular, roundish pores. From its lower half there arise three divergent curved pyramidal feet of about the same length. Mouth constricted, only one-third as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 diameter.

Habitat.—Atlantic, Stations 348 to 353, surface.

11. Lithomelissa haeckelii, Bütschli.

Lithomelissa haeckelii, Bütschli, 1883, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 517, Taf. xxxiii. fig. 23, a, b.

Shell rough, with sharp collar stricture. Relative length of the two joints = 6 : 5, breadth = 6 : 7. Cephalis subspherical, large, with two divergent horns, a very large, oblique pyramidal occipital horn on the summit, and a very small frontal horn on the middle of the forehead. Thorax campanulate, little larger than the cephalis, with regular circular pores of twice the breadth. From the upper part of the thorax, below the collar stricture, there arise three stout, divergent, angular, semi-lunar feet, about as long as the shell. Mouth wide open, not constricted.

Dimensions.—Cephalis 0.6 long, 0.6 broad; thorax 0.05 long, 0.07 broad.

Habitat.—Tropical Atlantic, Station 347, depth 2260 fathoms; fossil in Barbados.

12. Lithomelissa bütschlii, n. sp. (Pl. [56], fig. 1).

Shell smooth, with slight collar stricture. Relative length of the two joints = 5 : 6, breadth = 4 : 5. Cephalis ovate, large, with two small conical horns, which are opposed nearly horizontally, in the upper part of the cephalis; an anterior frontal and a posterior occipital horn. Thorax ovate, truncate, little larger. Pores of both joints irregular, roundish, of very different sizes. From the middle part of the thorax there arise three short conical divergent feet. (In the figured specimen there were some accessory thorns; in another specimen, found afterwards, the surface was quite smooth, but the two horns and the three feet much larger, half as long as the cephalis.)

Dimensions.—Cephalis 0.05 long, 0.04 broad; 0.06 long, 0.05 broad.

Habitat.—Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms.

Subgenus 3. Sethomelissa, Haeckel, 1881, Prodromus, p. 431.

Definition.—Cephalis with three, four, or more horns, a primary occipital, a secondary frontal, and one or more accessory parietal horns.

13. Lithomelissa corythium, Ehrenberg.

Lithomelissa corythium, Ehrenberg, 1875, Abhandl. d.k. Akad. d. Wiss. Berlin, p. 78, Taf. iii, fig. 12.

Shell smooth, with slight collar stricture. Relative length of the two joints = 4 : 3, breadth = 4 : 5. Cephalis campanulate, with three short conical horns on the summit. Thorax flat and wide. From its upper part below the collar stricture, there arise three divergent, pyramidal feet, fenestrated at the base, about as long as the shell. Mouth wide open. (The specimen figured by Ehrenberg was an incomplete one.)

Dimensions.—Cephalis 0.04 in diameter, thorax 0.03 long, 0.05 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; fossil in Barbados.

14. Lithomelissa decacantha, n. sp. (Pl. [56], fig. 2).

Sethomelissa decacantha, Haeckel, 1881, Prodromus et Atlas.

Shell smooth, with deep collar stricture, and with ten prismatic spines of nearly equal size and similar form. Relative length and breadth of the two joints about equal. Cephalis ovate, in the upper half hyaline, in the lower half with few scattered pores; in the equator with four prismatic horns of the same length, which diverge upwards; three of them are placed in the same meridional planes as the three wings and the three feet of the thorax (one occipital and two parietal); the fourth (frontal) horn is opposed to the occipital. Thorax campanulate, three-edged, with three vertical prominent feet (directed downward) and three horizontal wings, arising from their knees. Mouth wide open, not constricted.

Dimensions.—Cephalis 0.05 diameter; thorax 0.05 long, 0.06 broad.

Habitat.—Equatorial Atlantic, Station 347, surface.

Genus 538. Psilomelissa,[[155]] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three free lateral wings, or solid spines arising from the sides of the thorax. No terminal feet. Cephalis smooth, without a horn.

The genus Psilomelissa has the same formation of the shell as the nearly allied preceding genus Lithomelissa, and may be derived from it by reduction and loss of the cephalic horn. The cephalis is quite bare.

1. Psilomelissa galeata, Haeckel.

Dictyocephalus galeatus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. vii. fig. 25.

Shell smooth, with sharp collar stricture. Relative length of the two joints = 5 : 3, breadth = 4 : 5. Cephalis ovate, with numerous irregular, roundish pores. Thorax truncate, conical, with a few small pores. From its upper part (below the collar stricture) there arise three thin, bristle-shaped, widely divergent wings, about as long as the cephalis. Mouth widely open.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.03 long, 0.05 broad.

Habitat.—Western Tropical Pacific, Stations 200 to 225, surface.

2. Psilomelissa phalacra, n. sp.

Shell smooth, with deep collar stricture. Relative length of the two joints = 5 : 6, breadth = 4 : 4. Cephalis ovate, hyaline, with few small pores only in the lower third. Thorax cylindrical, truncate, with small irregular, roundish pores. From its upper third there arise below the stricture three club-shaped, nearly horizontally divergent wings, as long as the thorax. The cephalis and the three feet are similar to those of Peromelissa phalacra, (Pl. [57], fig. 11); but the cylindrical thorax with irregularly scattered pores is completely different, and exhibits a truncate, wide open mouth.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.04 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Psilomelissa hertwigii, Haeckel.

Lithomelissa hertwigii, Bütschli, 1882, Zeitschr. f. wiss. Zool., p. 517, Taf xxxiii. fig. 22, a, b.

Shell rough, with obliterated collar stricture. Length of the two joints = 4 : 4, breadth = 5 : 5. Cephalis hemispherical. Thorax little larger, cylindrical. From its upper half there arise three very strong pyramidal divergent wings, about as long as the shell. Pores of both joints very small and numerous, circular. Mouth truncate, wide open.

Dimensions.—Cephalis 0.04 long, 0.06 broad; thorax 0.04 long, 0.05 broad.

Habitat.—Fossil in Barbados.

4. Psilomelissa calvata, n. sp. (Pl. [56], fig. 3).

Shell smooth, with sharp collar stricture. Length of the two joints = 7 : 5, breadth = 5 : 6. Cephalis ovate, large, with subregular, circular, double-contoured pores. Thorax smaller, ovate, with very irregular, roundish pores of different sizes. From its upper third there arise three conical, slender, widely divergent spines or wings of the same length. (In fig. 3 the cephalis with the three wings is alone represented.)

Dimensions.—Cephalis 0.07 long, 0.05 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms.

5. Psilomelissa sphærocephala, n. sp.

Shell rough, with deep collar stricture. Length of the two joints = 1 : 2, breadth = 1 : 3. Cephalis spherical. Thorax cap-shaped, flat and broad. From its upper half there arise three pyramidal wings, half as long, fenestrated at the base and nearly horizontally divergent. Mouth constricted, half as broad as the thorax.

Dimensions.—Cephalis 0.03 diameter; thorax 0.06 long, 0.09 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 539. Spongomelissa,[[156]] n. gen.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three free lateral wings, or solid spines arising from the sides of the thorax. No terminal feet. Cephalis with one or more horns.

The genus Spongomelissa differs from its ancestral genus Lithomelissa only in the development of spongy framework in the shell-wall—a very rare production in the Cyrtoidea (compare Peripyramis, p. [1162], and Spongocyrtis, p. [1188]).

1. Spongomelissa spongiosa, Haeckel.

Lithomelissa spongiosa, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 519, 539, Taf. xxxiii. fig. 25, a, b, c.

Shell of dense spongy structure, with a deep collar stricture. The subspherical cephalis and the truncate abdomen of nearly equal size, both with irregular delicate spongy framework. Mouth wide open. Cephalis with a large vertical apical and a small oblique frontal horn. Thorax with three very stout, three-sided prismatic widely divergent lateral wings, which are covered with numerous irregularly ramified branches; the spongy framework arises by communication of the delicate branches.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Fossil in Barbados.

Genus 540. Clathrocanium,[[157]] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 829.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three prominent lateral ribs on the thorax, alternating with three large holes (or thoracic gates). Cephalis with a horn.

The genus Clathrocanium is nearly allied to Dictyophimus and Lithomelissa, and, together with these two genera, may be regarded as surviving representatives of the oldest and most primitive forms of Dicyrtida. It differs from the latter mainly in the incomplete fenestration of the shell, three large interradial holes remaining between the three perradial thoracic ribs. It may therefore be derived either from Euscenium or from Tripospyris by the development of a terminal lattice-band between the three feet. Clathrocanium may be divided into two different subgenera: Clathrocanidium, with simple horn and smooth mouth, and Clathrocorona, with fenestrated horn and coronated mouth.

Subgenus 1. Clathrocanidium, Haeckel.

Definition.—Horn of the cephalis simple, not fenestrated. Peristome smooth.

1. Clathrocanium squarrosum, Ehrenberg.

Clathrocanium squarrosum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vii. fig. 5.

Cephalis campanulate, with irregular roundish pores and a pyramidal horn of the same length, bearing at the apex three short branches. Length of the two joints 2 : 3, breadth = 2 : 6. Thorax with three simple, prismatic, thin ribs, which are twice as long as the cephalis, separated by large triangular holes and connected only at the distal end by a small triangular ring of delicate lattice-work. Peristome smooth, wide, as broad as the thorax.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.06 long, 0.12 broad.

Habitat.—Western Tropical Pacific (Philippine Sea), depth 3300 fathoms.

2. Clathrocanium sphærocephalum, n. sp. (Pl. [64], fig. 1).

Cephalis spherical, with regular circular pores and a prismatic horn of the same length, with three serrated edges. Length of the two joints = 2 : 3, breadth 2 : 4. Thorax with three broad, triangular, latticed, divergent ribs, which are separated by three large ovate holes (about as large as the cephalis), and connected at the distal end by a broad fenestrated circular ring of regular lattice-work (about six pores in its height). Peristome smooth, constricted, half as broad as the thorax.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Clathrocanium coarctatum, Ehrenberg.

Clathrocanium coarctatum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf vii. fig. 6.

Lychnocanium fenestratum, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 767.

Cephalis spherical, thorny, with regular circular pores and a simple pyramidal horn of the same length. Length of the two joints = 2 : 3, breadth = 2 : 5. Thorax with three simple, prismatic, little prominent ribs, which are separated by three large ovate holes (twice as long as the cephalis), and connected below the prominent distal end by a narrow circular ring of delicate lattice-work. Peristome smooth, wide, little narrower than the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.06 long, 0.1 broad.

Habitat.—Western Tropical Pacific (Philippine Sea), depth 3300 fathoms.

4. Clathrocanium triomma, n. sp. (Pl. [64], fig. 3).

Cephalis spherical, thorny, with regular circular pores, and a slender prismatic horn of twice the length, bearing at its apex three short recurved branches. Length of the two joints = 2 : 4, breadth = 2 : 5. Thorax with three broad prismatic, fenestrated ribs, which are separated by three large subcircular holes, and below the prominent distal end by a broad, triangular, roundish ring of subregular lattice-work (with square pores). Peristome smooth, about half as broad as the thorax.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Subgenus 2. Clathrocorona, Haeckel, 1881, Prodromus, p. 431.

Definition.—Horn of the cephalis fenestrated. Peristome on the margin of the basal mouth with a corona of spines.

5. Clathrocanium diadema, n. sp. (Pl. [64], fig. 2).

Clathrocorona diadema, Haeckel, 1881, Prodromus, p. 431.

Cephalis hemispherical, thorny, with irregular roundish pores, and a large prismatic horn of twice the length, the three edges of which are denticulate and fenestrated, each with a series of square pores. Length of the two joints = 1 : 3, breadth = 2 : 4. Thorax thorny, with three broad fenestrated divergent ribs, which are separated by three large ovate holes (twice as long as the cephalis) and have their prominent distal ends connected below by a broad circular ring of lattice-work (with irregular polygonal small meshes). Peristome wide, two-thirds as broad as the thorax, with a circular corona of small square pores and alternating prominent small teeth.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

6. Clathrocanium reginæ, n. sp. (Pl. [64], fig. 4).

Clathrocorona reginæ, Haeckel, 1881, Prodromus, p. 431.

Cephalis hemispherical, with irregular roundish pores and a prismatic club-shaped horn of twice the length, the three edges of which are denticulate and fenestrated. Length of the two joints = 1 : 3, breadth = 1 : 4. Thorax thorny, with three broad triangular, fenestrated and nodulated ribs, which are separated by three large ovate holes (twice as long as the cephalis) and have their prominent distal ends connected below by a circular ring of lattice-work. Peristome constricted, as broad as the thorax, with a corona of short spines.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.08 long, 0.12 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Genus 541. Lamprodiscus,[[158]] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 831.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three divergent lateral ribs in the wall of the flat, conical, discoidal, or pyramidal thorax. Cephalis with a horn. Peristome smooth, without corona of spines.

The genus Lamprodiscus, and the following nearly allied Lampromitra, differ from all preceding Sethopilida in the complete connection of the three thoracic feet by lattice-work, so that they are imbedded in the thorax-wall as prominent ribs and are not prolonged beyond the margin as free feet. The shell is commonly very flat, conical or pyramidal, sometimes nearly discoidal. The margin of Lamprodiscus is simple, smooth.

1. Lamprodiscus monoceros, Ehrenberg.

Lamprodiscus monoceros, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 295, Taf. vii. fig. 2.

Shell smooth, with deep collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 8. Cephalis spherical, hyaline, without pores, with an oblique conical horn of the same length. Thorax flat, campanulate, nearly hemispherical, with convex lateral outlines, and regular hexagonal meshes, increasing gradually in size towards the mouth. Bars very thin. Peristome smooth.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.16 broad.

Habitat.—Western Tropical Pacific (Philippine Sea), Station 200, surface.

2. Lamprodiscus coscinodiscus, Ehrenberg.

Lamprodiscus coscinodiscus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 295, Taf. vii. fig. 3.

Shell smooth, with sharp collar stricture. Thorax of the same form and structure as in the preceding species, differing from it mainly in the structure of the smooth circular margin, which is composed of a ring of very small square pores. Length of the two joints = 1 : 4, breadth = 1 : 8. Cephalis with small hexagonal pores, without horn or with a short rudimentary horn. Lateral outlines of the campanulate thorax in the upper part concave, in the lower convex.

Dimensions.—Cephalis 0.02 diameter; thorax 0.08 long, 0.16 broad.

Habitat.—Tropical Pacific, Stations 206, 224, 266, &c., surface.

3. Lamprodiscus tricostatus, n. sp.

Shell smooth with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 7. Cephalis spherical, with an oblique conical horn of twice the length and small circular pores. Thorax flatly conical, twice as broad as high, with straight lateral outline, and regular hexagonal meshes, increasing gradually in size towards the mouth; bars very thin. Peristome or margin of the basal mouth circular, smooth. Very similar to Theopilium tricostatum (Pl. [70], fig. 6), but without abdomen. Differs from the two preceding species mainly in the conical form of the thorax and the less delicate network.

Dimensions.—Cephalis 0.03 diameter; thorax 0.1 long, 0.2 broad.

Habitat.—Cosmopolitan, Mediterranean, Atlantic, Indian, Pacific; surface.

4. Lamprodiscus lævis, Haeckel.

Eucecryphalus lævis, R. Hertwig, 1879, Organism. d. Radiol., p. 77, Taf. viii. figs. 6, 6a, 6b.

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 6. Cephalis subspherical, with small circular pores and an oblique conical horn of twice the length. Thorax flat, pyramidal, twice as broad as long, with three strong, straight divergent edges and subregular roundish pores. Peristome smooth.

Dimensions.—Cephalis 0.025 diameter; thorax 0.08 long, 0.16 broad.

Habitat.—Mediterranean (Messina), R. Hertwig, surface.

Genus 542. Lampromitra, Haeckel,[[159]] 1881, Prodromus, p. 431.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three divergent lateral ribs in the wall of the flat conical or pyramidal thorax. Cephalis commonly with a horn. Peristome with a corona of spines.

The genus Lampromitra differs from the preceding and nearly allied Lamprodiscus only in the development of a dentated peristome, or an elegant corona of teeth around the wide open mouth. It bears therefore to the latter the same relation that Clathrocorona does to Clathrocanium.

1. Lampromitra coronata, n. sp. (Pl. [60], fig. 7, 7a).

Shell flat, conical, with slight collar stricture. Length of the two joints = 1 : 2, breadth = 2 : 7. Cephalis hemispherical, with a conical oblique horn of twice the length, and small subregular hexagonal pores. Thorax with larger, subregular, hexagonal meshes, six to eight times as broad as the bars. Peristome or basal margin of the thorax circular, with a marginal ring of smaller polygonal meshes and a triple coronal of short spines; two external rings of short conical centrifugal spines, and an internal ring of thin centripetal rods (fig. 7a). In fig. 7 the shell is seen from below and exhibits very distinctly the internal cross of the collar septum, composed of the four divergent cortinar bars; between the latter descend the four pear-shaped lobes of the central capsule (each containing an oil globule), whilst the apical part of the capsule (with the nucleus) is hidden in the large cap-shaped cephalis.

Dimensions.—Cephalis 0.03 long, 0.07 broad; thorax 0.06 long, 0.2 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Lampromitra quadricuspis (Pl. [58], fig. 7).

Shell flat, conical, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 2 : 10. Cephalis hemispherical, with subregular circular pores and an oblique, conical, occipital horn of twice the length, bearing three divergent lateral branches, which are directed upwards, and correspond to the three thoracic ribs. Further down, near the collar stricture, a short divergent frontal horn arises. Thorax with irregular roundish pores of different sizes, three to six times as broad as the bars. Peristome with a simple coronal of short, conical, divergent spines, about as long as the diameter of the cephalis.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.06 long, 0.2 broad.

Habitat.—North Atlantic, Canary Islands, surface.

3. Lampromitra furcata, n. sp. (Pl. [58], fig. 8).

Shell flat, conical, with deep collar stricture, very similar in form and structure to the preceding species; differs from it in the shape of the peristome and the armature of the cephalis, which bears a conical, forked, occipital horn of the same length, and a small rudimentary divergent frontal horn. Length of the two joints = 1 : 2, breadth = 1 : 6. The four pores of the collar septum (two larger cardinal and two smaller jugular) exhibit in this species a peculiar asymmetry (fig. 8). The peristome bears a simple coronal of spines as long as the diameter of the cephalis. The major part of them is forked, some irregularly branched.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.18 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

4. Lampromitra pyramidalis, n. sp.

Shell flat, pyramidal, smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 9. Cephalis subspherical, with an oblique pyramidal horn of twice the length, and small circular pores. Thorax with three strong, divergent, straight ribs and three flat triangular sides between them, with subregular hexagonal pores, increasing in size towards the mouth. Peristome with a simple coronal of large and numerous divergent, conical spines, half as long as the shell.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.09 long, 0.18 broad.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

5. Lampromitra huxleyi, Haeckel (Pl. [59], fig. 1).

Eucecryphalus huxleyi, Haeckel, 1879, Natürl. Schöpfungsgesch., Edit. vii. Taf. xvi. fig. 9.

Shell flat, conical, spiny, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 8. Cephalis hemispherical, with a short conical horn of the same length. Thorax with irregular polygonal pores. Peristome with three coronals of divergent bristle-shaped spines; the first directed obliquely upwards, the second outwards, and the third nearly vertically, downwards; the bristles of the latter are much longer, about as long as the height of the shell.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.16 broad.

Habitat.—Australia (east coast), Station 169, surface.

6. Lampromitra schultzei, Haeckel.

Eucecryphalus schultzei, Haeckel, 1862, Monogr. d. Radiol., p. 309, Taf. v. figs. 16-19.

Shell flat, conical, smooth, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 8. Cephalis hemispherical, with a small conical horn of half the length, and very small roundish pores. Thorax with three strong, straight ribs and irregular polygonal pores, which are much larger in the middle part than in the upper or lower part. Peristome with a double coronal of short, conical, divergent spines; the superior obliquely ascending, the inferior vertically descending. (Named in honour of the late Professor Max Schultze, the illustrious histologist.)

Dimensions.—Cephalis 0.025 diameter; thorax 0.07 long, 0.2 broad.

Habitat.—Mediterranean, Messina, surface.

7. Lampromitra arborescens, n. sp, (Pl. [60], fig. 8, 8a).

Shell flat, pyramidal, spiny, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 2 : 10. Cephalis cap-shaped, with an oblique, slender, conical horn of twice the length, and small circular pores. Thorax with three slight almost obliterated ribs and three vaulted sides between them, with irregular roundish pores. The three ribs are distinct in the proximal, not in the distal part. Peristome with a double coronal of smaller squarish pores and numerous divergent spines; the larger spines are irregularly branched and as long as the diameter of the cephalis.

Dimensions.—Cephalis 0.15 long, 0.03 broad; thorax 0.04 long, 0.2 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

8. Lampromitra dendrocorona, n. sp. (Pl. [58], fig. 9).

Shell flat, conical, with smooth surface and deep collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 10. Cephalis hemispherical, with a slender occipital horn of three times the length, and a small divergent frontal horn. Thorax with three strong prominent straight ribs and irregular polygonal meshes, increasing in size towards the mouth. Peristome with a dense coronal of numerous short conical spines and twenty-four to thirty larger arborescent spines, longer than the diameter of the cephalis.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 543. Callimitra,[[160]] Haeckel, Prodromus, 1881, p. 431.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three vertical latticed wings, which stretch between the three divergent lateral ribs of the thorax and the vertical horn of the cephalis. No frontal horn.

The genus Callimitra, and the two following nearly allied genera, Clathromitra and Clathrocorys, form together a peculiar small group, the Callimitrida, living in the Central Pacific, and differing from the other Sethopilida in some remarkable points, derived perhaps directly from the Archiscenida, Archiscenium and Pteroscenium, by the development of thoracic network between the three cortinar feet. In the centre of the collar septum, where these feet are united, there arises a vertical free columella, prolonged over the top of the cephalis as a free horn, and this horn is connected with the three thoracic ribs by three vertical fenestrated wings.

1. Callimitra carolotæ, n. sp. (Pl. [63], figs. 1, 7, 8).

Cephalis campanulate, conical, with irregular, polygonal pores, and a thin bristle-shaped apical horn of the same length. Length of the two joints = 3 : 6, breadth = 2 : 6. Thorax in the upper half with irregular network, in the lower half with parallel transverse bars; in each of its three sides descend two convergent pairs of stronger, parallel, curved ribs, not confluent at the peristome. Each of the three vertical wings with eight stronger ribs, three arising from the cephalis, five from each foot. Dedicated to my dear mother Charlotte Sethe.

Dimensions.—Cephalis 0.07 long, 0.05 broad; thorax 0.15 long, 0.15 broad.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

2. Callimitra annæ, n. sp. (Pl. [63], fig. 2).

Cephalis campanulate, conical, with irregular, polygonal pores, and a thin bristle-shaped horn of the same length. Length of the two joints = 1 : 2, breadth = 1 : 3. Thorax nearly in its whole extent with parallel transverse bars, which are crossed by two convergent systems of parallel beams; in each of its three sides descend four convergent pairs of stronger, parallel, curved ribs, not confluent at the peristome. Each of the three vertical wings with six stronger ribs, three arising from the cephalis, three from each foot. Dedicated to my dear first wife Anna Sethe.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.12 long, 0.18 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

3. Callimitra agnesæ, n. sp. (Pl. [63], fig. 5).

Cephalis pear-shaped, with irregular, square pores, and a slender bristle-shaped horn twice as long. Length of the two joints = 1 : 3, breadth = 1 : 5. Thorax in its whole extent with parallel transverse bars, which are crossed by two converging and crossed systems of parallel beams; in each of its three sides descend five convergent pairs of stronger, parallel, curved ribs, the two or three upper of which are crossed at the peristome. Each of the three vertical wings with five stronger ribs, three arising from the cephalis and the horn, two from each foot. Dedicated to my dear second wife Agnes Huschke.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.15 long, 0.22 broad.

Habitat.—Central Pacific, Station 273, depth 2350 fathoms.

4. Callimitra elisabethæ, n. sp. (Pl. [63], fig. 6).

Cephalis nearly hemispherical, with irregular square pores, and a strong prismatic horn thrice the length. Length of the two joints = 2 : 7, breadth = 2 : 9. Thorax in the upper third with irregular network, in the lower two-thirds with parallel transverse bars which are crossed by two convergent systems of parallel beams; in each of its three sides descend three convergent pairs of stronger, parallel, curved ribs; the two ribs of the uppermost pair are united and confluent in a single odd rib in the lower half of the thorax. Each of the three vertical wings with seven stronger ribs, three arising from the cephalis and the horn, four from each foot. Dedicated to my dear elder daughter Elizabeth Haeckel.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.15 long, 0.2 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Callimitra emmæ, n. sp. (Pl. [63], figs. 3, 4).

Cephalis campanulate, with irregular, polygonal pores, and very thin bars (of the same shape as in the thorax) and with a thin bristle-shaped horn twice the length. Length of the three joints = 3 : 6, breadth = 2 : 9. Thorax in its whole extent with an arachnoidal network similar to that in the cephalis and the three wings, composed of very numerous parallel threads, which are crossed by two crossed diagonal systems of parallel threads. In each of the three sides of the thorax descend five convergent pairs of stronger ribs, the three upper of which are crossed and form large rhomboidal meshes. Each of the three vertical wings with ten stronger ribs, four arising from the cephalis and each horn, six from each foot. Dedicated to my dear younger daughter Emma Haeckel.

Dimensions.—Cephalis 0.07 long, 0.06 broad; thorax 0.15 long, 0.22 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Genus 544. Clathromitra,[[161]] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three vertical latticed wings, which stretch between the three divergent lateral ribs of the thorax and the vertical horn of the cephalis. The front of the latter is armed with a large frontal horn.

The genus Clathromitra differs from the preceding similar Callimitra in the development of a free frontal or sternal horn, a prolongation of an internal obliquely ascending rod, opposite to the caudal foot. Therefore the shell in this genus possesses five divergent free spines, two cephalic horns, and three thoracic feet. The lattice-work of the three vertical wings is not so delicate as in Callimitra.

1. Clathromitra pterophormis, n. sp. (Pl. [57], fig. 8).

Cephalis very large, hemispherical, about as long and half as broad as the three-sided pyramidal thorax; both with irregular, polygonal meshes. Apical horn three to four times as long as the frontal horn and the three basal feet. All five spines three-sided prismatic, with nearly smooth edges. Three lateral wings half as broad as the cephalis.

Dimensions.—Cephalis 0.05 long, 0.1 broad; thorax 0.05 long, 0.15 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Clathromitra pentacantha, n. sp.

Cephalis large, hemispherical, half as long as the three-sided pyramidal thorax; both with irregular, roundish meshes. Apical horn of about the same length as the frontal horn, and twice as long as the three basal feet. All five spines three-sided prismatic, with denticulated edges. Three lateral wings about as broad as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.08 broad; thorax 0.1 long, 0.2 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Genus 545. Clathrocorys,[[162]] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three prominent lateral ribs on the thorax, alternating with three large holes (or thoracic gates). The three ribs are connected with the central apical horn of the cephalis by three vertical latticed wings.

The genus Clathrocorys differs from the two preceding nearly allied genera in the incomplete fenestration of the thorax, the three perradial ribs of which are separated by three large interradial holes. It has therefore the same relation to Callimitra that Clathrocanium bears to Dictyophimus.

1. Clathrocorys murrayi, n. sp. (Pl. [64], fig. 8).

Cephalis pear-shaped, with irregularly square pores. From the centre of its base there arise four strong, prismatic, radial beams of nearly equal size, the vertical, straight, cephalic horn being little longer than the three divergent, somewhat curved feet. In the three meridional planes (between the horn and each foot) a few rather thick branches arise, which by communication of the ramules form the three vertical latticed wings; each wing with two large meshes, three to five meshes of medium size, and three to four parallel arachnoidal rows of small, square, distal meshes. The three walls of the flat pyramidal thorax (between every two feet) are formed in the upper part by squarish network similar to that of the cephalis, in the middle part by a single row of arches separated by thin threads, and in the lower part by a narrow band of arachnoidal network. Dedicated to Dr. John Murray.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.04 long, 0.15 broad; apical distance of every two feet 0.15, of each foot and the horn 0.17.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Clathrocorys teuscheri, n. sp. (Pl. [64], fig. 10).

Cephalis pear-shaped, with irregular, square pores. From the centre of its base there arise seven prismatic, radial beams of equal strength, supporting the lattice-work of the wall; the single vertical beam is prolonged into the apical horn; six others lie in the three meridian planes (between the horn and each foot); three ascending end in the wall of the cephalis, three descending are prolonged into the three strong feet, which are longer than the horn. In each meridional plane there arise four thicker and several thinner bars, which by communication of their ramules form the three latticed wings; each wing with a single very large mesh, two meshes of medium size, and a narrow marginal band of small, square pores. The three walls of the flat pyramidal thorax are formed in the upper part by squarish network similar to that of the cephalis, in the lower part by a narrow band of the same; between them a large hole. Dedicated to Dr. Reinhold Teuscher.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.15 broad; apical distance of every two feet 0.2, of each foot and the horn 0.2.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Clathrocorys giltschii, n. sp. (Pl. [64], fig. 9).

Cephalis pear-shaped, with irregular, polygonal pores. From the centre of its base there arise seven prismatic, radial beams of different strength; the single vertical beam bears six lateral branches (parallel to the three ascending supporting beams), and is prolonged into the apical horn; six others lie in the three meridional planes (between the horn and each foot); three weaker ascending beams end in the wall of the cephalis, three stronger descending are prolonged into the three large diverging feet, which are twice as long as the cephalic horn. The network of the three wings and of the three-sided pyramidal thorax is about the same as in the preceding species, but much more developed; the marginal bands with the squarish network are much broader, and an arachnoidal wicker-work of very thin thread-like bars fills out the large meshes. Dedicated to Mr. Adolf Giltsch.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.12 long, 0.2 broad; apical distance of every two feet 0.24, of each foot and the horn 0.2.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Genus 546. Eucecryphalus,[[163]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 836.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three free collar wings or solid spines arising from the collar stricture, and freely prominent between the horned cephalis and the flat conical thorax.

The genus Eucecryphalus, according to the restricted definition here given, comprises only those Sethopilida in which the three primary cortinar beams are perfectly free divergent collar wings, i.e., free spines arising outside the shell from the collar stricture, between the cephalis and thorax. The type of this genus (which I formerly united with other Sethopilida) remains Eucecryphalus gegenbauri.

Subgenus 1. Eucyrtomphalus, Haeckel, 1881, Prodromus, p. 431.

Definition.—Peristome or margin of the basal mouth of the thorax smooth, without marginal spines.

1. Eucecryphalus corocalyptra, n. sp.

Shell flatly conical, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 6. Cephalis subspherical, with an oblique conical horn twice its length. Thorax conical, twice as broad as long, with regular hexagonal meshes and straight lateral outlines. From the collar stricture there arise three slender conical spines, about as long as the thorax, divergent downwards. Similar to Corocalyptra agnesæ (Pl. [59], fig. 3), but without lumbar stricture and abdomen. Peristome or basal margin of the mouth of the thorax smooth, simple.

Dimensions.—Cephalis 0.3 diameter; thorax 0.09 long, 0.18 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, surface.

2. Eucecryphalus halicalyptra, n. sp.

Shell flat, campanulate, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 10. Cephalis hemispherical, with two divergent conical horns, a major occipital and a minor frontal horn. Thorax with subregular hexagonal meshes and concave-convex lateral outlines, campanulate. From the collar stricture there arise three divergent bristle-shaped spines, nearly horizontal, about half as long as the thorax. Peristome smooth, with a marginal coronal of small square pores.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.2 broad.

Habitat.—Central Pacific, Stations 266 to 274, surface.

Subgenus 2. Eucecryphalium, Haeckel.

Definition.—Peristome or margin of the basal mouth of the thorax dentate, with a coronal of marginal spines.

3. Eucecryphalus cuvieri, n. sp.

Shell flatly conical, with slight collar stricture. Length of the two joints = 1 : 8, breadth = 2 : 10. Cephalis hemispherical, with an oblique pyramidal horn twice as long. Thorax with straight outlines and regular hexagonal meshes, increasing in size towards the mouth. From the collar stricture there arise three stout conical spines, half as long as the thorax, and diverging downwards. Peristome with a ring of small square pores and alternate conical divergent spines. Differs from the similar Clathrocyclas alcmenæ (Pl. [59], fig. 6), mainly in the simple apical horn and the possession of the three collar fundamental spines.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.15 long, 0.2 broad.

Habitat.—Tropical Atlantic, Station 342, depth 1445 fathoms.

4. Eucecryphalus mülleri, n. sp.

Shell flatly campanulate, of nearly the same structure as and similar form to that of the preceding species. Differs from it mainly in the considerable size of the cephalic horn and the three collar spines, which are bristle-shaped and longer than the shell. Length of the two joints = 1 : 4, breadth = 2 : 8. The peristome bears a double marginal ring of divergent conical spines, the upper being directed upwards, the lower downwards.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.08 long, 0.16 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

5. Eucecryphalus gegenbauri, Haeckel.

Eucecryphalus gegenbauri, Haeckel, 1862, Monogr. d. Radiol., p. 308, Taf. v. figs. 12-15.

Eucecryphalus gegenbauri, R. Hertwig, 1879, Organism. d. Radiol., p. 76, Taf. viii. figs. 5, 5a, 5b.

Shell flatly conical, campanulate, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 8. Cephalis hemispherical, with a conical horn of the same length, and very small pores. Thorax about twice as broad as high, with large, subregular, hexagonal meshes, increasing in size downwards. In the upper half of the thorax the meshes are filled up by an extremely delicate arachnoidal network. From the collar stricture there arise three divergent bristle-shaped spines half as long as the thorax. Peristome with a double coronal of small square pores (the inner smaller and more numerous than the outer), and with a single coronal of divergent marginal spines. This cosmopolitan species is rather variable.

Dimensions.—Cephalis 0.02 to 0.03 diameter; thorax 0.1 to 0.12 long, 0.02 to 0.25 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

6. Eucecryphalus campanella, Haeckel.

Pterocodon campanella, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, Taf. xix. fig. 2.

Shell campanulate, conical, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 2. Cephalis hemispherical, with a short conical horn half as long, and very small pores. Thorax campanulate, as broad as high, with large roundish meshes, increasing in size downwards. From the collar stricture arise three strong, divergent, somewhat curved spines, nearly as long as the thorax. Peristome with a coronal of ten to twelve strong, conical, marginal spines, which are nearly parallel, directed downwards, a little curved, and half as long as the thorax. In the complete specimen examined by me, the apical horn, the three lateral wings and twelve terminal feet were well preserved.

Dimensions.—Cephalis 0.02 to 0.03 diameter; thorax 0.06 to 0.07 long and broad.

Habitat.—Fossil in Barbados.

Genus 547. Amphiplecta,[[164]] Haeckel, 1881, Prodromus, p. 424.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta) with three internal thoracic ribs, enveloped by the network of the thorax. Cephalis with a large apical opening, surrounded by a coronal of spines.

The genus Amphiplecta (or Amphicryphalus) comprises some very peculiar forms of Sethopilida, probably widely remote from the other genera of this subfamily, and derived directly from the Plectanida (compare above, p. [921]). The cortinar tripodium, composed of three feet divergent downwards, and one apical horn ascending upwards (in some species also a second frontal horn) is here enclosed in the cavity of a two-jointed shell, which exhibits two large openings, a smaller apical hole in the top of the cephalis, and a larger terminal mouth on the thorax. There is no trace of a sagittal ring.

1. Amphiplecta amphistoma, n. sp.

Cephalis subspherical, spiny, with sharp collar stricture on the base; its apical opening central, surrounded by a coronal of twelve to eighteen short spines. Length of the two joints = 7 : 8, breadth = 6 : 20. Thorax flatly conical, armed with bristle-shaped spines. Meshes of the network in both joints subregular, hexagonal, six to eight times as broad as the bars. Basal mouth bristly.

Dimensions.—Cephalis 0.07 long, 0.06 broad; thorax 0.08 long, 0.2 broad.

Habitat.—Central Pacific, Station 274, surface.

2. Amphiplecta acrostoma, n. sp. (Pl. [97], fig. 10).

Cephalis subspherical, spiny, with distinct collar stricture on the base, its apical opening central, surrounded by a coronal of six to nine divergent denticulate spines. Length of the two joints = 5 : 6, breadth = 4 : 15. Thorax flatly conical, armed with denticulate spines. Meshes of both joints irregular, polygonal, twice to six times as broad as the bars. Basal mouth armed with longer, divergent, denticulate spines.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.15 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Amphiplecta callistoma, n. sp. (Pl. [59], fig. 2).

Cephalis flat, cap-shaped, spiny, with obliterated collar stricture on the base; its apical opening excentric, oblique, surrounded by a coronal of ten to twenty bristle-shaped spines. Length of the two joints = 4 : 5, breadth = 7 : 25. Thorax flatly conical, armed with long bristle-shaped spines. Meshes of both joints irregular, hexagonal, twice to six times as broad as the bars. Basal mouth with a double irregular coronal of small square pores, and of bristle-shaped divergent spines.

Dimensions.—Cephalis 0.04 long, 0.07 broad; thorax 0.05 long, 0.25 broad.

Habitat.—Central Pacific, Station 271, surface.

Genus 548. Lychnocanium,[[165]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta), with three solid terminal feet on the peristome. No thoracic ribs. Cephalis with a horn.

The genus Lychnocanium, very rich in common living and fossil forms, comprises those Sethopilida in which the thorax bears three simple terminal feet around the mouth, but no lateral ribs in its wall. It has therefore been probably derived from Dictyophimus by reduction and loss of these three lateral ribs. The mouth is commonly more or less constricted. The three feet surrounding it are sometimes divergent, straight or curved, at other times parallel and vertical, straight, or curved and convergent. The central capsule exhibited in some living species three or four distinct lobes, filling up the upper half of the thorax.

Subgenus 1. Lychnocanella, Haeckel.

Definition.—Feet divergent, straight or scarcely curved; their terminal distance greater than their basal distance.

1. Lychnocanium lanterna, n. sp. (Pl. [61], fig. 7).

Shell conical, rough, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis with a stout pyramidal horn of the same length. Thorax pear-shaped, twice as broad as the constricted mouth, with regular, circular pores of the same breadth as the bars. Three feet pyramidal, little divergent, straight, about as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Stations 263 to 268, depth 2650 to 2900 fathoms.

2. Lychnocanium continuum, Ehrenberg.

Lychnocanium continuum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 11.

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical with a conical horn of the same length. Thorax pear-shaped, twice as broad as the constricted mouth, nearly hyaline, with a very small number of scattered minute pores. Three feet pyramidal, little divergent, straight, about as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

Habitat.—Fossil in Barbados.

3. Lychnocanium pyriforme, n. sp. (Pl. [61], fig. 11).

Shell pear-shaped, rough, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis hemispherical, with a conical horn of the same length. Thorax inflated, four times as broad as the constricted tubular mouth, with regular, circular pores. Three feet pyramidal, straight, divergent, about as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.12 long, 0.15 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, many Stations; also fossil in Barbados.

4. Lychnocanium favosum, n. sp. (Pl. [61], fig. 6).

Shell campanulate, rough, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis hemispherical, with a rudimentary pyramidal horn of half the length. Thorax subglobular, three times as broad as the constricted mouth, with regular, circular pores, and an elevated hexagonal framework between them. Three feet cylindrical, slender, straight, divergent, twice to three times as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

5. Lychnocanium nodosum, n. sp. (Pl. [61], fig. 14).

Shell campanulate, nodose, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a rudimentary conical horn of half the length. Thorax nearly hemispherical, twice as broad as the flat mouth, with regular, circular pores, and a variable number of scattered, conical, fenestrated protuberances. Three feet very large, prismatic, straight, divergent, twice as long as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.12 broad.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

6. Lychnocanium carinatum, Ehrenberg.

Lychnocanium carinatum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 5.

Shell campanulate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subglobular, with a slender horn of the same length. Thorax conical, twice as broad as the flat mouth, with fifteen to twenty prominent, longitudinal, divergent ribs, alternating with the same number of rows of pores. Three feet slender, prismatic, straight, divergent, twice as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

Habitat.—Fossil in Barbados.

7. Lychnocanium ventricosum, Ehrenberg.

Lychnocanium ventricosum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 12.

Shell pear-shaped, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a stout conical horn twice the length. Thorax conical, three times as broad as the constricted mouth, with irregular, roundish pores of different sizes. Three feet stout, conical, divergent, half as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; fossil in Barbados.

8. Lychnocanium tribulus, Ehrenberg.

Lychnocanium tribulus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 1.

Shell pear-shaped, nodose, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis subglobular, with a conical horn twice the length. Thorax ovate, twice as broad as the constricted mouth, with irregular, roundish pores of different sizes. Three stout feet strongly divergent, pyramidal, about as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.02 broad; 0.08 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Lychnocanissa, Haeckel.

Definition.—Feet divergent, more or less curved; their terminal distance greater than their basal distance.

9. Lychnocanium fortipes, n. sp. (Pl. [61], fig. 12).

Shell inflated, rough, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis small, hemispherical, with a pyramidal horn of half the length. Thorax subglobular, truncate, twice as broad as the constricted mouth, with large, regular, circular pores and very thin bars. Three feet very stout, prismatic, twice as long as the thorax, widely divergent, curved with convexity outwards, club-shaped at the distal end, with denticulate edges.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

10. Lychnocanium falciferum, Ehrenberg.

Lychnocanium falciferum, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 7; Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 4.

Lithomelissa falcifera, Haeckel, 1862, Monogr. d. Radiol., p. 303.

Shell inflated, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis small, with a conical horn of half the length. Thorax subglobular, truncate, three times as broad as the constricted mouth, with small, regular, circular pores. Three feet widely divergent, twice as long as the thorax, curved like a crescent, with strong convexity outwards.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

Habitat.—Fossil in Barbados.

11. Lychnocanium tuberosum, n. sp. (Pl. [61], fig. 13).

Shell conical, tuberculate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subglobular, with a conical horn of the same length. Thorax inflated, twice as broad as the flat mouth, with small, irregular, roundish pores and scattered fenestrated tubercles. Three feet very large, angular, three times as long as the thorax, curved like a crescent, with strong convexity outwards.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.12 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

12. Lychnocanium hirundo, Ehrenberg.

Lychnocanium hirundo, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 8.

Lithornithium hirundo, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 53.

Lithocampe hirundo, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 65.

Shell conical, tuberculate, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis hemispherical, with a conical horn of half the length. Thorax campanulate, twice as broad as the flat mouth, with longitudinal, divergent ribs, alternating with rows of small circular pores. Three feet divergent, striated, gradually lessening from a broad base, twice as long as the thorax, curved like a crescent, with convexity outwards.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Tertiary rocks of Barbados and the Mediterranean (Sicily, Greece).

13. Lychnocanium fenestratum, n. sp. (Pl. [61], fig. 10).

Shell pear-shaped, rough, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subglobular, with a very large prismatic horn, which is about as long as the shell, with three denticulate, prominent, wing-like crests, which are pierced by a series of pores. Thorax ovate, three times as broad as the constricted, prominent mouth, with subregular, circular pores. Three feet arising somewhat above the mouth, prismatic, with denticulate edges, about as long as the thorax, divergent, curved, with convexity outwards.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

14. Lychnocanium sigmopodium, n. sp. (Pl. [61], fig. 15).

? Lychnocanium tetrapodium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 3.

Shell campanulate, rough with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a slender pyramidal horn twice the length. Thorax inflated, conical, with regular circular pores and a wide open mouth of nearly the same breadth. Three feet widely divergent, twice as long as the thorax, angular, S-shaped, or curved with convexity inwards. (Lychnocanium tetrapodium of Ehrenberg is perhaps a variety of this species?).

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, many stations at various depths; also fossil in Barbados and Sicily.

15. Lychnocanium trichopus, Ehrenberg.

Lychnocanium trichopus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 5.

Shell conical, smooth, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical, with a rudimentary conical horn of half the length. Thorax campanulate, with regular, circular pores and wide open mouth of nearly the same breadth. Three feet divergent, very slender, four to five times as long as the thorax, not broader than one pore, S-shaped, or curved with convexity inwards in the distal half.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Fossil in Barbados.

Subgenus 3. Lychnocanoma, Haeckel.

Definition.—Feet parallel, vertical, straight, or little curved; divergent in the basal half, often convergent in the distal half; their terminal distance about equal to the basal distance.

16. Lychnocanium tripodium, Ehrenberg.

Lychnocanium tripodium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 2.

Shell ovate, smooth, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis subglobular, with a slender conical horn twice the length. Thorax inflated, twice as broad as the constricted mouth, with small, regular, circular pores. Three feet slender, prismatic, twice to three times as long as the thorax, nearly straight and parallel, vertical.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.07 long, 0.07 broad.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.

17. Lychnocanium cypselus, Ehrenberg.

Lychnocanium cypselus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 10.

Shell slender, ovate, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a conical horn of the same length. Thorax ovate, truncate, three times as broad as the narrow, constricted mouth, with small, regular, circular pores. Three feet slender, somewhat shorter than the thorax, little curved, with convexity outwards, nearly parallel, vertical. (In the specimen figured by Ehrenberg, the third foot was broken off.)

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Fossil in Barbados.

18. Lychnocanium ovatum, n. sp.

Shell ovate, rough, without external collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 5. Cephalis conical, with a stout conical horn of the same length. Thorax ovate, four times as broad as the narrow constricted mouth, with small, regular, circular pores, separated by hexagonal frames of twice the breadth. Three feet cylindrical, half as long as the thorax, and three times as long as broad, straight, parallel, vertical.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax, 0.12 long, 0.1 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

19. Lychnocanium crassipes, Ehrenberg.

Lychnocanium crassipes, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 7.

Shell campanulate, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a thin conical horn of the same length. Thorax semi-ovate, three times as broad as the narrow constricted mouth, with fifteen to twenty divergent, denticulate ribs, alternating with the same number of rows of small, regular, circular pores. Three feet very stout, as long as the thorax, cylindrical, nearly straight and parallel, vertical, at the distal end clavate, spinulate or a little forked.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

20. Lychnocanium clavigerum, n. sp. (Pl. [61], fig. 4).

Shell campanulate, sulcate, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subglobular, with a spindle-shaped papillate horn twice the length. Thorax nearly spherical, truncate at both poles, three times as broad as the narrow, constricted, somewhat tubular mouth, with fifteen to twenty elevated meridional ribs, alternating with the same number of rows of circular pores. Three feet slender, cylindrical, twice as long as the thorax, in the basal half divergent, in the distal half convergent, club-shaped, with a thickened papillate end.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.08 long, 0.01 broad.

Habitat.—Indian Ocean, Madagascar, surface (Rabbe).

21. Lychnocanium pudicum, n. sp. (Pl. [61], fig. 2).

Shell campanulate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis hemispherical, hyaline (without pores), with a short and thick club-shaped, spinulate horn of the same length. Thorax subglobular, truncate at both poles, twice as broad as the constricted mouth, with small, irregular, roundish pores. Three feet somewhat shorter than the thorax, curved like a crescent, with convexity outwards; their distal ends club-shaped, spinulate, convergent towards the central axis.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.06 long, 0.07 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 549. Lychnodictyum,[[166]] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta), with three latticed terminal feet on the peristome, without thoracic ribs. Cephalis originally with a horn (sometimes lost).

The genus Lychnodictyum differs from the preceding Lychnocanium only in the fenestration of the three terminal feet, and bears therefore to it the same relation that the ancestral Tripocyrtis does to Dictyophimus.

1. Lychnodictyum challengeri, Haeckel.

Dictyopodium challengeri, Wyville Thomson, 1877, Atlantic, vol. i. p. 234, fig. 52.

Dictyophimus (vel Tripocyrtis) challengeri, Haeckel, 1878, Protistenreich, p. 47, fig. 35.

Shell campanulate, smooth, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a large, oblique, pyramidal horn thrice the length. Thorax with three inflated bosoms between the three decurrent ribs, which are prolonged into three vertical, parallel, pyramidal, in the upper half fenestrated feet, as long as the thorax. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

Dimensions.—Cephalis 0.03 diameter; thorax 0.08 long, 0.12 broad.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.

2. Lychnodictyum wyvillei, n. sp.

Shell pyramidal, smooth, with obliterated collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 5. Cephalis subspherical, with a large, straight, pyramidal horn of twice the length. Thorax nearly tetrahedral, inflated, with three rounded, decurrent ribs, which are prolonged into three widely divergent, angular, curved feet, about as long as the shell, with pyramidal fenestrated base. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

Dimensions.—Cephalis 0.025 diameter; thorax 0.08 long, 0.12 broad.

Habitat.—Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms.

3. Lychnodictyum scaphopodium, n. sp. (Pl. [56], fig. 4).

Cephalis hemispherical, large, without horn, with irregular, small, roundish pores. Thorax a little larger, campanulate, with three broad, shovel-shaped, fenestrated, vertical feet, and larger, irregular pores. In the figured specimen the third (posterior) foot was broken off. In another specimen the three feet were somewhat longer and not so broad.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

4. Lychnodictyum sethopodium, n. sp.

Cephalis hemispherical, large, with a rudimentary conical horn, and very scarce small pores. Thorax twice as broad and long as the cephalis, campanulate, with irregular, roundish pores, and three slender, pyramidal, divergent feet twice the length, which in the upper half are fenestrated, in the lower half solid.

Dimensions.—Cephalis 0.025 long, 0.045 broad; thorax 0.05 long, 0.09 broad.

Habitat.—South Atlantic, Station 330, surface.

Subfamily 2. Sethoperida, Haeckel, 1881, Prodromus, p. 433.

Definition.—Tripocyrtida with the basal mouth of the shell fenestrated (vel Dicyrtida triradiata clausa).

Genus 550. Sethopera,[[167]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the latticed wall of the thorax. Cephalis with a horn.

The genus Sethopera is probably the oldest form of the Sethoperida, and may therefore be regarded as the common ancestral form of this subfamily. The thorax exhibits three radial ribs, which are completely enclosed in its wall. Sethopera may be derived either from Dictyophimus or from another of the Sethopilida (Lamprodiscus, Clathrocanium) by development of a basal lattice-plate closing the mouth. There are often wide holes or open spaces between the three radial ribs.

1. Sethopera tricostata, n. sp. (Pl. [97], fig. 11).

Cephalis subspherical, spinulate, with a pyramidal horn of the same length. Length of the two joints = 5 : 8, breadth = 5 : 8. Thorax also nearly spherical; in the upper half with three stout, prismatic, convex, divergent ribs, and three large ovate holes between them; in the lower half with numerous small and irregular pores, spinulate.

Dimensions.—Cephalis 0.05 diameter; thorax 0.08 diameter.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Sethopera oceania, Haeckel.

Lithopera oceania, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. iv. fig. 21.

Cephalis hemispherical, with a small bristle-shaped horn of half the length (broken off in Ehrenberg's figure). Length of the two joints = 3 : 4, breadth = 3 : 4. Thorax nearly spherical; in the upper half with three divergent ribs, separated by some larger, irregular pores; in the lower half with numerous small, irregular, roundish pores.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.04 long, 0.04 broad.

Habitat.—North Atlantic, Station 354, surface; Canary Islands and Azores.

3. Sethopera pyrum, Haeckel.

? Lithopera pyrum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297.

Cephalis hemispherical, with a small conical horn of half the length. Length of the two joints = 3 : 10, breadth = 3 : 7. Thorax pear-shaped, with rather large, regular, quincuncial pores; its upper half with three divergent ribs in the wall, half as broad as the subspherical lower half. (The three ribs probably were overlooked by Ehrenberg.)

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.1 long, 0.07 broad.

Habitat.—North Pacific, Station 256, surface; Californian Sea, 2600 fathoms, Ehrenberg.

4. Sethopera lagena, Haeckel.

Lithopera lagena, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 4.

Cephalis pear-shaped, with a small conical horn of half the length. Length of the two joints = 3 : 8, breadth = 3 : 6. Thorax smooth, pear-shaped, with irregular roundish pores; in the wall of its upper third three divergent thin ribs (sometimes wanting); the lower half inflated. (Compare Sethocapsa lagena.)

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Fossil in Barbados.

Genus 551. Lithopera,[[168]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the cavity of the thorax. Cephalis with a horn.

The genus Lithopera is, like the preceding Sethopera, one of the most simple and oldest forms of the Sethoperida, and exhibits three divergent thoracic ribs, which are prolonged neither into lateral wings nor into basal feet. But whilst in Sethopera the three ribs are enclosed in the lattice-work of the shell-wall, in Lithopera they lie freely in its cavity, and are overgrown by the enveloping shell-wall, being inserted on its inner face with their distal ends. Lithopera may be derived directly from Lithomelissa, by development of lattice-work closing the shell-mouth. Therefore the lower part of the cephalis is hidden in the uppermost part of the thorax; only its upper part is free.

1. Lithopera bacca, Ehrenberg.

Lithopera bacca, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 1.

Cephalis spherical, with small, irregular pores and a bristle-shaped spine of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 6, breadth = 1 : 5. Thorax ellipsoidal, smooth, with regular, hexagonal, small pores, and very thin, thread-like bars. From the deep collar stricture there arise three internal, divergent bars, which are inserted at the uppermost third of the thorax.

Dimensions.—Cephalis 0.02 diameter; thorax 0.12 long, 0.1 broad.

Habitat.—Tropical Pacific, Stations 200, 224, 266, 271, &c., surface.

2. Lithopera bursella, Ehrenberg.

Lithopera bursella, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. x. fig. 4.

Shell of about the same form and structure as in the nearly allied preceding species, but smaller, of more slender form, with smaller pores and thinner bars. Length of the two joints = 1 : 5, breadth = 1 : 3. In the specimen observed by me the three internal, divergent bars of the ellipsoidal thorax (not seen by Ehrenberg) were as distinct as in the similar preceding and following species.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.06 broad.

Habitat.—Indian Ocean, Zanzibar (Pullen), Madagascar (Rabbe), surface.

3. Lithopera ananassa, n. sp. (Pl. [57], fig. 3).

Shell of about the same form and structure as in the two preceding species, but larger and more robust, and differing in the spiny surface. Length of the two joints = 1 : 5, breadth = 1 : 4. Here also the lower half of the spherical cephalis is submerged in the ellipsoidal thorax, and from the collar stricture arise three strong, internal, divergent beams. The bars of the hexagonal pores are much thicker than in the two preceding species.

Dimensions.—Cephalis 0.03 diameter; thorax 0.16 long, 0.12 broad.

Habitat.—Tropical Atlantic, Stations 347 to 352, surface.

4. Lithopera globosa, n. sp.

Cephalis spherical, very small, with two divergent conical horns of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 5, breadth = 1 : 5. Thorax spherical, with regular, circular, hexagonally-framed pores. From the collar stricture arise three radial internal beams, horizontally diverging, and inserted at the inside of the thorax.

Dimensions.—Cephalis 0.03 diameter; thorax 0.15 diameter.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

5. Lithopera gutta, Ehrenberg.

Lithopera gutta, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 2.

Shell pear-shaped, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis spherical, with a conical horn of the same length; its lower half hidden in the uppermost part of the ovate thorax, and connected with its wall by three internal, cortinar beams. Pores of the thorax very irregular in form and size, partly lobed.

Dimensions.—Cephalis 0.02 diameter; thorax 0.08 long, 0.06 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms; Philippine Sea (depth 3300 fathoms), Ehrenberg.

Genus 552. Micromelissa,[[169]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent, solid, lateral wings. Cephalis with a horn.

The genus Micromelissa differs from the two preceding genera in the free prominence of the three cortinar ribs, forming three solid lateral wings. Beyond these the thorax walls are convergent, and the basal mouth closed by a lattice-plate. Therefore Micromelissa may have arisen from Lithomelissa simply by development of this basal mouth-plate.

1. Micromelissa bombus, n. sp. (Pl. [57], fig. 14).

Shell smooth, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis spherical, with an oblique conical horn of the same length. Thorax subspherical, in the upper half with three conical, downwardly diverging wings, about as long as its radius. Pores very small and scarce.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.09 long, 0.1 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Micromelissa vespa, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 2 : 5, breadth = 2 : 3. Cephalis spherical, with an oblique pyramidal horn twice the length. Thorax inversely ovate, in the upper half with three pyramidal wings, which are equal to its breadth, little curved and diverging downwards. Pores very small and scarce.

Dimensions.—Cephalis 0.04 diameter; thorax 0.1 long, 0.06 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Micromelissa apis, n. sp.

Shell rough, with deep collar stricture. Length of the two joints = 2 : 3, breadth = 2 : 4. Cephalis subspherical, with a straight conical horn of half the length, and subregular, circular, double-contoured pores, of the same breadth as the bars. Thorax little larger, subspherical, with irregular, roundish pores, twice to four times as broad as the bars. From its lower half arise three short conical wings, curved downwards, and half as long as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.06 long, 0.08 broad.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

4. Micromelissa microptera, Haeckel.

Lithomelissa microptera, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 2; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 78, Taf. iii. fig. 13.

Lithomelissa microptera, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxiii. fig. 26.

Shell smooth, with distinct collar stricture. Length of the two joints = 4 : 6, breadth = 3 : 5. Cephalis ovate, with a straight sword-shaped horn of the same length and very small pores, some larger ones above the stricture. Thorax little larger, ovate, nearly hyaline, with very few and small scattered pores. From its uppermost part arise three short conical wings, scarcely half as long as the cephalic horn, little curved and divergent downwards.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.06 long, 0.05 broad.

Habitat.—Fossil in Barbados.

5. Micromelissa ventricosa, Haeckel.

Lithomelissa ventricosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 11.

Shell rough, with slight collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 5. Cephalis small, hemispherical, with a small conical horn of half the length. Thorax ovate, very large, papillate, with irregular, roundish pores. From its basal part arise three short and stout conical wings at great distances, shorter than the cephalis. (A transition-form to Sethocapsa.)

Dimensions.—Cephalis 0.02 long, 0.022 broad; thorax 0.14 long, 0.11 broad.

Habitat.—Fossil in Barbados.

Genus 553. Peromelissa,[[170]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three divergent solid lateral wings. Cephalis without horn.

The genus Peromelissa differs from the preceding ancestral form, Micromelissa, only in the absence of the cephalic horn, which is lost by reduction.

1. Peromelissa phalacra, n. sp. (Pl. [57], fig. 11).

Shell smooth, with two joints of nearly equal size and similar ovate form. Cephalis in the upper half hyaline, without pores; in the lower half with four remote, transverse rows of irregular, roundish pores, decreasing in size towards the hemispherical summit. Thorax with twelve transverse rows of pores, the upper six rows three to four times as large as the lower six rows. From its upper half diverge almost horizontally three angular club-shaped wings, half as long as the shell.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.06 long, 0.05 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Peromelissa psilocrana, n. sp.

Shell smooth, very similar to the preceding species in size and form, but differing from it in the disposition of the irregular, roundish pores, which are irregularly scattered, and in the form of the three wings, which are slender, pyramidal, diverging downwards, and about as long as the entire shell.

Dimensions.—Cephalis 0.07 long, 0.06 broad; thorax 0.07 long, 0.06 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Peromelissa capito, Haeckel.

Lithomelissa capito, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 14.

Shell rough, with two joints of nearly equal size and similar ovate form. Pores irregular, roundish, everywhere scattered. From the upper half of the thorax arise three short conical wings, which are little curved and diverge downwards (scarcely half as long as the breadth of the shell).

Dimensions.—Cephalis 0.07 long, 0.06 broad; thorax 0.07 long, 0.06 broad.

Habitat.—Fossil in Barbados.

4. Peromelissa calva, n. sp. (Pl. [57], fig. 12).

Shell rough, with two ovate joints of somewhat different sizes. Pores irregular, roundish, everywhere scattered. Thorax little larger than the cephalis; from its upper half arise three short conical wings, diverging downwardly or nearly horizontally.

Dimensions.—Cephalis 0.06 long, 0.04 broad; thorax 0.07 long, 0.05 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Genus 554. Sethomelissa,[[171]] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three divergent latticed lateral wings. Cephalis with a horn (or a bunch of horns).

The genus Sethomelissa differs from the nearly allied Micromelissa in the fenestration of the three lateral wings, and may be derived either from this genus by development of lattice-work connecting the three wings with the shell, or perhaps from Clathrocanium by closing the mouth.

1. Sethomelissa hymenoptera, n. sp.

Cephalis subspherical, thorny, with a bunch of three divergent, larger apical spines. Thorax pear-shaped, with three broad, triangular, latticed wings, the superior edge of which is a horizontal, straight, and stout spine, nearly as long as the thorax. Pores irregular, roundish.

Dimensions.—Cephalis 0.03 diameter; thorax 0.11 long, 0.08 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 555. Tetrahedrina,[[172]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with a three-sided pyramidal thorax, the three edges of which are prolonged into three divergent, solid, terminal feet. Cephalis with a horn.

The genus Tetrahedrina, and the two following nearly allied genera, are distinguished by the possession of three free, divergent, terminal feet, projecting over the latticed mouth of the thorax. Tetrahedrina may be derived directly from Dictyophimus, by development of a horizontal latticed mouth-plate from the middle part of the feet, the lower part of which remains free. This genus, not noticed by Ehrenberg, is similar to his Lithochytris, and common in the Barbados deposits.

1. Tetrahedrina pyramidalis, n. sp.

Shell three-sided pyramidal, smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis hemispherical, with small, sparsely disposed pores, and a pyramidal horn of the same length. Thorax with subregular, circular pores and three sharp edges, prolonged into three divergent pyramidal feet of the same length.

Dimensions.—Cephalis 0.03 diameter; thorax 0.12 long, 0.12 broad.

Habitat.—Fossil in Barbados.

2. Tetrahedrina pyriformis, n. sp.

Shell pear-shaped, rough, with distinct collar stricture. Length of the two joints = 2 : 6, breadth = 2 : 5. Cephalis subspherical, with a conical horn of the same length. Thorax with subregular, circular pores, ovate, at the broad base with three pyramidal, widely divergent feet of the same length. (Similar to Lychnocanium tribulus, Ehrenberg, 1875, loc. cit., pl. vii. fig. 1, but with the mouth closed by a lattice-plate.)

Dimensions.—Cephalis 0.04 diameter; thorax 0.12 long, 0.1 broad,

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

3. Tetrahedrina quadricornis, Haeckel.

Lithochytris triangula, Bury, 1862, Polycystins of Barbados, pl. xix. figs. 4, 5, 6.

Shell pear-shaped, papillate, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, with a stout conical horn twice the length. Thorax with irregular, roundish, lobulated pores, with three conical, stout, divergent feet at the base, of the same size and form as the cephalic horn.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Genus 556. Sethochytris,[[173]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three terminal latticed feet or hollow, fenestrated, divergent, basal apophyses of the thorax. Cephalis with a horn.

The genus Sethochytris differs from the preceding Tetrahedrina in the fenestration of the three basal feet, which form direct protrusions or evaginations of the three basal corners of the pyramidal shell. It may be derived from Sethopera by centrifugal growth of the basal corners.

1. Sethochytris triconiscus, n. sp. (Pl. [57], fig. 13).

Shell rough, with deep collar stricture. Length of the two joints = 1 : 8, breadth = 1 : 3. Cephalis spherical, with an oblique pyramidal horn of the same length. Thorax campanulate, conical; its three basal corners prolonged into three divergent, slender, hollow, fenestrated cones, twice as long as the thorax, and ending in a stout pyramidal spine.

Dimensions.—Cephalis 0.04 diameter, thorax 0.12 diameter, length of the feet 0.2.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

2. Sethochytris barbadensis, Haeckel.

Lithochytris barbadensis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160, Taf. v. fig. 2.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 4. Cephalis ovate, with a conical horn of half the length. Thorax conical; its base prolonged into three divergent, hollow, fenestrated cones, half as long as the thorax. Pores small, subregular, circular.

Dimensions.—Cephalis 0.025 diameter, thorax 0.1 diameter, length of the feet 0.05.

Habitat.—Fossil in Barbados.

3. Sethochytris pyramis, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 8, breadth = 1 : 5. Cephalis ovate, with a conical horn of half the length. Thorax pyramidal, with three sharp edges; its base prolonged into three pyramidal, divergent, hollow, fenestrated feet, nearly as long as the thorax. Pores regular, circular, double-contoured.

Dimensions.—Cephalis 0.04 diameter; thorax 0.2 diameter, length of the feet 0.15.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; also fossil in Barbados.

4. Sethochytris triangula, Haeckel.

Lithochytris triangula, Bury, 1862, Polycystins of Barbados, pl. xix. fig. 7.

Shell rough, with obliterated collar stricture (but distinct internal collar septum). Length of the two joints = 1 : 6, breadth = 1 : 3. Cephalis subspherical, with a stout conical horn of the same length. Thorax pear-shaped, inflated; its base prolonged into three divergent, hollow, fenestrated cones, about as long as the thorax. Pores regular, circular.

Dimensions.—Cephalis 0.03 diameter; thorax 0.09 diameter, length of the feet 0.1.

Habitat.—Fossil in Barbados.

Genus 557. Clathrolychnus,[[174]] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three vertical, lateral latticed wings stretched between the apical horn and the three terminal feet. The external lattice-work connecting the wings and closing the mouth forms an arachnoidal mantle around the shell.

The genus Clathrolychnus may be derived directly from Clathrocorys, by development of an external arachnoidal mantle connecting the three wings and the three feet, and enveloping the whole shell, closing at the same time the basal mouth of the thorax by a fenestrated plate.

1. Clathrolychnus araneosus, n. sp. (Pl. [64], fig. 5).

Cephalis subspherical, with irregular, polygonal pores and a large pyramidal horn of twice the length. Length of the two joints = 4 : 9, breadth = 5 : 12. Thorax with three large triangular holes (twice as broad as the cephalis) between the three pyramidal, divergent feet, which at the distal end are connected by a narrow band of network, composed of two or three rows of polygonal pores. The entire pyramidal shell is enveloped by a very delicate web of irregular, polygonal meshes, closing also the basal mouth. (In fig. 5 the greater part of the web is taken off to demonstrate the large holes of the thorax). Only two feet are visible.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.09 long, 0.12 broad.

Habitat.—Central Pacific, Station 274, surface.

2. Clathrolychnus periplectus, n. sp. (Pl. [64], fig. 6).

Cephalis subspherical, with subregular, circular pores and a pyramidal horn of the same length. Length of the two joints = 1 : 2, breadth = 1 : 3. Thorax with three large elliptical holes between the three pyramidal, divergent feet, which are connected at the distal end by a broad band of network, composed of five to ten rows of polygonal pores. The entire pyramidal shell is enveloped by a very delicate web, which on the sides is composed of subregular, square meshes, and on the closed mouth of polygonal meshes. (In fig. 6 only a part of the web is represented.)

Dimensions.—0.04 long, 0.05 broad; thorax 0.08 long, 0.14 broad.

Habitat..—Central Pacific, Station 271, surface.

Family LXIII. Anthocyrtida, n. fam.

Sethophormida et Sethophænida, Haeckel, 1881, Prodromus, p. 432, 433.

Definition.—Dicyrtida multiradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, and bearing numerous—four to nine or more—radial apophyses.)

The family Anthocyrtida, composed of the Sethophormida and Sethophænida of my Prodromus, comprises those Cyrtoidea in which the shell is two-jointed and bears numerous radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethophormida is a simple, wide opening; in the Sethophænida closed by a lattice-plate.

Numerous fossil and living forms of Anthocyrtida were described formerly by Ehrenberg in his genera Carpocanium and Anthocyrtis. These, however, represent only a small part of the whole family, which exhibits a great variety in the composition of the lattice-work and in the number of radial beams. The number of species here described amounts to one hundred and forty, and these are disposed in fourteen genera (twelve Sethophormida and two Sethophænida).

The Sethophormida may be again divided into two different groups or tribes, the Sethamphorida and Carpocanida; in the former the thorax bears numerous radial ribs, enclosed in its wall; in the latter these ribs have disappeared, and only a corona of terminal feet is developed around the mouth. The shell of the former is usually pyramidal, with a widely open mouth; of the latter ovate, with a constricted mouth. The mouth of the thorax becomes perfectly closed in the Sethophænida.

The majority of the Anthocyrtida may be derived from the Polyspyrida (Petalospyris, &c.) by reduction of the cephalis and loss of the sagittal ring, as was suggested by Bütschli (1882, loc. cit.). But another part may also have arisen from the Tripocyrtida, by interpolation of secondary radial apophyses between the three primary perradial apophyses. The cephalis in this family is developed in all possible degrees, from one of a considerable size to one very much reduced. If it becomes perfectly lost, the Cyrtocalpida arise.

Synopsis of the Genera of Anthocyrtida.

I. Subfamily Sethophormida.

Terminal mouth of the thorax a simple wide opening.

Radial ribs smooth (rarely thorny) enclosed in the wall of the thorax (cephalis commonly small, without horns).Shell flat, campanulate or nearly discoidal (cephalis without horn),558. Sethophormis.
Shell ovate, with constricted mouth (without horn),559. Sethamphora.
Shell slender pyramidal, with straight ribs.Meshes of the network simple,560. Sethopyramis.
Meshes fenestrated by secondary latticework,561. Plectopyramis.
Meshes closed by spongy framework,562. Spongopyramis.
Radial ribs thorny (rarely smooth) prolonged into free terminal feet (cephalis commonly large, with one or more horns).Shell not enveloped by arachnoidal network,563. Acanthocorys.
Shell enveloped by arachnoidal network,564. Arachnocorys.
No ribs in the thorax. Peristome with free terminal feet.Cephalis well-developed with an apical horn.Feet terminal, without separate peristome.Six feet,565. Anthocyrtoma.
Nine feet,566. Anthocyrtis.
Twelve or more feet,567. Anthocyrtium.
Feet subterminal, outside the constricted peristome,568. Anthocyrtidium.
Cephalis rudimentary, hidden in the upper part of the thorax, without horn,569. Carpocanium.

II. Subfamily Sethophænida.

Terminal mouth closed by a lattice-plate.

Thorax with lateral apophyses (four to six or more wings),570. Sethophæna.
Thorax with terminal apophyses (four to six or more feet),571. Clistophæna.

I. Subfamily Sethophormida.

Terminal mouth of the thorax a simple wide opening.

Radial ribs smooth (rarely thorny) enclosed in the wall of the thorax (cephalis commonly small, without horns).
Shell flat, campanulate or nearly discoidal (cephalis without horn),
558. Sethophormis.
Shell ovate, with constricted mouth (without horn),
559. Sethamphora.
Shell slender pyramidal, with straight ribs.
Meshes of the network simple,
560. Sethopyramis.
Meshes fenestrated by secondary latticework,
561. Plectopyramis.
Meshes closed by spongy framework,
562. Spongopyramis.
Radial ribs thorny (rarely smooth) prolonged into free terminal feet (cephalis commonly large, with one or more horns).
Shell not enveloped by arachnoidal network,
563. Acanthocorys.
Shell enveloped by arachnoidal network,
564. Arachnocorys.
No ribs in the thorax. Peristome with free terminal feet.
Cephalis well-developed with an apical horn.
Feet terminal, without separate peristome.
Six feet,
565. Anthocyrtoma.
Nine feet,
566. Anthocyrtis.
Twelve or more feet,
567. Anthocyrtium.
Feet subterminal, outside the constricted peristome,
568. Anthocyrtidium.
Cephalis rudimentary, hidden in the upper part of the thorax, without horn,
569. Carpocanium.

II. Subfamily Sethophænida.

Terminal mouth closed by a lattice-plate.

Thorax with lateral apophyses (four to six or more wings),
570. Sethophæna.
Thorax with terminal apophyses (four to six or more feet),
571. Clistophæna.

Subfamily 1. Sethophormida, Haeckel, 1881, Prodromus, p. 432.

Definition.—Anthocyrtida with the basal mouth of the shell open (vel Dicyrtida multiradiata aperta).

Genus 558. Sethophormis, Haeckel,[[175]] 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the flat and broad campanulate or nearly discoidal thorax. Cephalis also flat and broad, cap-shaped without horn.

The genus Sethophormis comprises a great number of widely distributed and large Dicyrtida, all agreeing in the flat cap-shaped or nearly discoidal form of the thorax, which has constantly a very delicate network, and is pierced by numerous radial beams. Four of these are commonly primary and direct prolongations of the four cortinar rods in the collar septum, whilst the others are secondary or interpolated ribs. Sethophormis may be derived either from the triradial Lamprodiscus by multiplication of the ribs (or interpolation of secondary ribs between the three primary), or from Halicalyptra by development of transverse rods connecting its terminal feet, and forming a ribbed thorax. Corresponding to the number of the ribs, we may distinguish as subgenera (separate genera in my Prodromus, 1881, p. 432) Tetraphormis with four, Pentaphormis with five, Hexaphormis with six, Octophormis with eight, Enneaphormis with nine, and Astrophormis with ten to twenty or more ribs. The cephalis bears no horn, and is usually large, flat, cap-shaped or hemispherical.

Subgenus 1. Tetraphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with four radial ribs opposite in pairs in two meridional planes, perpendicular to one another. Collar septum with four large pores.

1. Sethophormis cruciata, n. sp.

Cephalis very large, hemispherical with irregular, delicate network of small square meshes. Thorax flatly campanulate, with delicate, regular network of small hexagonal meshes. All bars very thin, thread-like. Four stout radial thoracic ribs, crossed in pairs, lie in two meridional planes, perpendicular to one another. Very similar to Sethophormis aurelia (Pl. [55], figs. 3, 4), but not so flat, and with only four thoracic ribs. Peristome or margin of the thoracic mouth smooth, circular.

Dimensions.—Cephalis 0.04 long, 0.08 broad; thorax 0.12 long, 0.36 broad.

Habitat.—Central Pacific, Station 271, surface.

2. Sethophormis medusa, n. sp.

Cephalis very large, flat, cap-shaped, with irregular, delicate network of polygonal meshes. Thorax flat, campanulate, nearly hemispherical, with delicate, irregular network of small polygonal meshes. All bars very thin, thread-like. Four stout radial thoracic ribs, as in the preceding species. Peristome denticulate.

Dimensions.—Cephalis 0.03 long, 0.09 broad; thorax 0.15 long, 0.25 broad.

Habitat.—North Pacific, Station 244, surface.

Subgenus 2. Pentaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with five radial ribs, one of the three primary ribs (the odd occipital rib) being simple, the two others (the paired lateral ribs) forked.

3. Sethophormis pentalactis, n. sp. (Pl. [56], fig. 5).

Cephalis large, flat, hemispherical, with subregular, hexagonal pores. Thorax flat, campanulate, nearly hemispherical; also with subregular, hexagonal pores, and with five stout ribs. The three primary ribs of the thorax are complete, and reach the peristome; the two secondary ribs (as basal branches of the two lateral ribs) are incomplete and absent in the distal half of the thorax. Peristome denticulate, with an elegant marginal corona of small square pores and short conical spines.

Dimensions.—Cephalis 0.03 long, 0.06 broad; thorax 0.1 long, 0.2 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

4. Sethophormis asteriscus, n. sp.

Cephalis large, flat, cap-shaped, with irregular polygonal pores. Thorax flat, campanulate, with subregular, hexagonal pores, and five stout ribs. The marginal distance between the two anterior (lateral) ribs is twice as great as the distance between every two other ribs (the postero-lateral ribs being basal branches of the antero-lateral ribs). Peristome with a double corona of short, conical spines.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.06 long, 0.17 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Sethophormis astrodiscus, n. sp.

Cephalis small, flatly vaulted, cap-shaped with irregular polygonal pores. Thorax very flatly vaulted, nearly discoidal, with subregular hexagonal pores, and five stout ribs. The marginal distance between all five ribs is nearly equal. Peristome denticulate with an elegant corona of small square pores and short conical thorns.

Dimensions.—Cephalis 0.015 long, 0.035 broad; thorax 0.05 long, 0.2 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Subgenus 3. Hexaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with six radial ribs (three primary perradial and three secondary interradial beams).

6. Sethophormis hexalactis, n. sp. (Pl. [56], fig. 6).

Cephalis large, hemispherical, with irregular, polygonal pores. Thorax flatly campanulate, with subregular, hexagonal pores, and six stout radial ribs; the lateral connected in pairs. (Fig. 6 exhibits the central part of the shell, seen from below.) In the subcircular collar septum the two anterior (jugular) meshes are much smaller than the two posterior (cardinal) meshes. The odd anterior (sternal) rib is opposite to the posterior (caudal) rib. The two paired ribs of each side (antero-lateral or pectoral and postero-lateral or ventral ribs) diverge from one common point. In the specimen figured the left half of the thorax exhibited the two regular ribs, and the right half three, a posterior accessory branch being developed (transition to Octophormis). This specimen might indeed be called Heptaphormis heptalactis.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.08 long, 0.22 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

7. Sethophormis hexagonalis, n. sp.

Cephalis small, flat, cap-shaped, with small, regular, hexagonal pores. Thorax flatly conical, nearly discoidal, with larger pores of the same form, and six stout, straight, prominent ribs. These arise at equal distances from the six corners of the hexagonal base of the collar septum. Peristome hexagonal, with a corona of short spines.

Dimensions.—Cephalis 0.015 long, 0.04 broad; thorax 0.06 long, 0.24 broad.

Habitat.—North Atlantic, Station 354, surface.

Subgenus 4. Octophormis, Haeckel.

Definition.—Thorax with eight radial ribs, four secondary interradial beams being interpolated between the four primary perradial beams of Tetraphormis.

8. Sethophormis octalactis, n. sp.

Cephalis large, hemispherical, with irregular, polygonal pores. Thorax flatly campanulate, with regular, hexagonal pores, and eight stout, regularly-disposed, radial ribs reaching the margin at equal distances. Four of these correspond to the four primary ribs of Tetraphormis cruciata, and exhibit at their base a larger pair of basal pores, surrounded by a semicircular ring (Pl. [70], fig. 5); the other four are secondary, interpolated. Peristome circular, simple.

Dimensions.—Cephalis 0.03 long, 0.06 broad; thorax 0.1 long, 0.22 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

Subgenus 5. Enneaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with nine radial ribs, three of which are the primary beams, the other six being secondary and interpolated.

9. Sethophormis rotula, n. sp. (Pl. [57], fig. 9).

Enneaphormis rotula, Haeckel, 1881, Prodromus et Atlas, pl. lvii. fig. 9.

Cephalis very large, flat, cap-shaped, trilobed, with irregular, polygonal network. Horizontal collar-ring stout, hexagonal, with three larger and three alternate smaller sides of half the length. From the middle of the three larger sides arise three horizontal, centripetal, radial beams, which are united in the centre of the collar-septum—the three primary cortinar beams. These are prolonged outside into three centrifugal primary ribs of the thorax. From the six corners of the collar-ring arise six other secondary, thoracic ribs, equal in size and similar in form to the three primary. Each of these nine equal, straight ribs of the thorax is thickened towards the distal end, and bears at equal distances five pairs of opposite (tangential) lateral branches. The opposite branches of the neighbouring spines become united, and lie nearly horizontally in one plane, so that the flat, discoidal thorax is like a nine-angled wheel with nine equally distant spokes and five concentric, nine-angled rings.

Dimensions.—Cephalis 0.12 diameter, thorax 0.36 diameter.

Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

10. Sethophormis triloba, n. sp.

Cephalis large, hemispherical, distinctly trilobed, with dense, irregular, polygonal network. From the centre of its top diverge three stout arches or semilunar rods, which are curved downwards, and unite with the three horizontal, radial beams of the collar-septum inside the collar-ring. These three parietal arches of the cephalis are much stronger than in the similar preceding species (Pl. [57], fig. 9), and between them are placed three vaulted bosoms of the cephalis. The collar-ring and the thorax are of the same form as in the preceding, but possess only four concentric, nine-angled rings.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.24 diameter.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

11. Sethophormis enneastrum, n. sp.

Cephalis very large, flat, cap-shaped, with hexagonal base, trilobed, of similar form and structure to the two preceding species. The flat, discoidal thorax has also the same form, with nine stout ribs and five concentric, nine-angled rings; its forty-five large meshes, however, are not so simple as these (Pl. [57], fig. 9), but are subdivided into irregular, smaller meshes by interpolated radial beams connecting the concentric rings.

Dimensions.—Cephalis 0.1 diameter, thorax 0.3 diameter.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

12. Sethophormis arachnium, n. sp.

Cephalis very large, flat, cap-shaped, trilobed, with hexagonal base, of the same structure as in the three preceding species. The flat discoidal thorax is also similar, and has the same structure as in the preceding species (Pl. [57], fig. 9); but the number of concentric, nine-angled rings is raised from five to eight, and in its outer part nine secondary radial beams are interpolated between the nine primaries, so that the peristome has not nine but eighteen corners.

Dimensions.—Cephalis 0.08 diameter, thorax 0.4 diameter.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

13. Sethophormis enneactis, n. sp.

Cephalis small, hemispherical, with small, irregular, polygonal pores. Thorax flatly pyramidal, nearly discoidal, with nine prominent, stout ribs, which are connected by numerous (twelve to sixteen) horizontal, nine-angled rings. In the outer half of the thorax there are nine weaker secondary ribs interpolated between the nine stronger primaries, and eighteen shorter and feebler tertiary ribs between the former and the latter. Peristome denticulated, nine-angled.

Dimensions.—Cephalis 0.03 diameter, thorax 0.08 long, 0.24 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

14. Sethophormis eupilium, n. sp. (Pl. [56], fig. 9).

Sethopyramis eupilium, Haeckel, 1882, Atlas, pl. lvi. fig. 9.

Craspedilium eupilium, Haeckel, 1878, Manuscript.

Cephalis very small, hemispherical, hyaline, without pores. Thorax flatly pyramidal, with nine concave, triangular faces and nine little curved, stout, radial beams. Between these are interpolated numerous incomplete secondary beams, which are absent in the apical part of the thorax. The radial beams being connected by numerous (thirty to forty or more) horizontal, ring-like threads, a delicate arachnoidal network with small, quadrangular pores is produced. Peristome nine-angled, with a peculiar vertical gallery, composed of four horizontal, parallel, nine-angled rings, which are connected by numerous vertical, parallel bars, therefore with three transverse rows of square pores. This peculiar species is very different from the preceding and may represent a separate genus, Craspedilium.

Dimensions.—Cephalis 0.01 diameter, thorax 0.1 long, 0.25 broad.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 6. Astrophormis, Haeckel.

Definition.—Thorax with a variable number of radial ribs (twelve to twenty or more).

15. Sethophormis aurelia, n. sp. (Pl. [55], figs. 3, 4).

Leptarachnium aurelia, Haeckel, 1879, Manuscript et Atlas.

Cephalis large, nearly hemispherical, with irregular, delicate network of small square meshes. Collar-septum with four large meshes, separated by a cross of four bars, opposite in pairs. Thorax flatly campanulate, with delicate, subregular, hexagonal meshes, and twenty-four prominent radial ribs; four of these are primary or perradial (centrifugal prolongations of the four bars of the collar-septum); four others are interradial or secondary, alternating with the former at angles of 45°; sixteen others are adradial or tertiary, interpolated between the first and second more or less irregularly. In some specimens the disposition of the twenty-four ribs was more regular, in others more irregular, than in the specimen figured (figs. 3, 4). The central capsule (fig. 4) exhibits a flat, cap-shaped part with the nucleus (enclosed in the cephalis), and four large, pear-shaped lobes protruded through the four large collar holes (somewhat deformed in the preparation figured). The wall of the thorax exhibits at the base four larger, nearly semicircular pores, bisected by the four primary thoracic ribs. Peristome with twenty-four indentations (between the prominent distal ends of the twenty-four ribs), often more distinct than in the specimen figured.

Dimensions.—Cephalis 0.03 long, 0.08 broad; thorax 0.1 to 0.2 long, 0.4 to 0.6 broad.

Habitat.—Central Pacific, Station 263 to 274, depth 2350 to 2925 fathoms.

16. Sethophormis dodecaster, n. sp. (Pl. [56], fig. 12).

Cephalis small, flatly cap-shaped, with irregular, small, roundish pores. Thorax flatly conical, nearly of the same shape as in the preceding species, but only with twelve prominent ribs; four primary or perradial ribs (as prolongations of the four crossed cortinar bars), and eight adradial ribs interpolated between the former, and arising at some distance from the collar ring. Peristome with twelve prominent pointed lobes (supported by the distal ends of the twelve ribs), and with twelve semicircular bosoms between them. (The specimen figured is young and not fully developed.)

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.1 long, 0.3 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

17. Sethophormis umbrella, n. sp. (Pl. [70], figs. 4, 5).

Cephalis large, flatly cap-shaped, with irregular, small polygonal meshes. Thorax flat, umbrella-shaped, with subregular, hexagonal meshes, and sixteen strong radial ribs. Four of these are perradial, and centrifugal prolongations of the four crossed collar beams; four others are interradial, and arise, alternating with the former, directly from the horizontal collar ring; eight ribs are adradial or tertiary, and arise in pairs from the four large perradial basal arches of the thorax, which become bisected by the four primary ribs. Peristome irregularly denticulate.

Dimensions.—Cephalis 0.02 long, 0.06 broad; thorax 0.12 long, 0.32 broad.

Habitat.—North Pacific (off Japan), Stations 236 to 239, surface.

18. Sethophormis floscula, n. sp.

Cephalis small, hemispherical, with subregular, small hexagonal pores. Thorax flatly conical, with larger hexagonal meshes and twenty-four ribs; four of these are perradial and prolongations of the four collar bars; four interradial arise from the collar ring between the former, alternating with them. Each of these eight main ribs gives off two more or less irregular, lateral branches (one at each side), altogether sixteen. The thorax is similar to Cladarachnium ramosum (Pl. [55], fig. 5), whilst the cephalis is quite different. Peristome with twenty-four prominent triangular lobes.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.1 long, 0.4 broad.

Habitat.—South Atlantic, Station 325, surface.

19. Sethophormis leptoscenium, n. sp.

Cephalis very small, spherical, with few small, circular pores. Thorax flatly conical or tent-shaped, with concave lateral outlines, small hexagonal meshes, and numerous (thirty to forty or more) strong, little curved, simple radial ribs. Peristome nearly circular, with a corona of small, irregular, conical spines.

Dimensions.—Cephalis 0.015 diameter; thorax 0.07 long, 0.26 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

20. Sethophormis leptopilium, n. sp.

Cephalis very small, subspherical, hyaline, without pores. Thorax flatly conical or hat-shaped, with concave lateral outlines, and a very delicate network of small square meshes (similar to Litharachnium araneosum, Pl. [55], fig. 8). This is supported by thirty-two curved radial ribs, four of which are primary, four secondary, and the other twenty-four interpolated. Peristome horizontally expanded and little recurved, like the reflexed brim of a hat.

Dimensions.—Cephalis 0.12 diameter; thorax 0.08 long, 0.24 broad.

Habitat.—South Pacific, Station 291, depth 2250 fathoms.

Genus 559. Sethamphora,[[176]] n. gen.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous curved ribs in the wall of the ovate thorax, the small mouth of which is constricted. Cephalis without horn.

The genus Sethamphora differs from the preceding Sethophormis, and from the next following ribbed Sethophormida, mainly in the small, more or less constricted mouth; therefore the thorax is more or less ovate, and its ribs curved, with the convexity external. Sethophormis may be divided into two different subgenera, Dictyoprora and Cryptocephalus; in the former the cephalis is perfectly free and well developed, in the latter it is more or less hidden in the uppermost part of the thorax (like Carpocanium).

Subgenus 1. Dictyoprona, Haeckel, 1881, Prodromus, p. 430.

Definition.—Cephalis large, perfectly free, not hidden in the thorax.

1. Sethamphora hexapleura, n. sp.

Shell ovate, smooth, with distinct collar stricture. Length of the two joints = 3 : 11, breadth = 5 : 10. Cephalis large, free, hemispherical, with small circular pores. Thorax truncate, ovate, with six strong curved ribs, and six large triangular meshes between them in the upper half; five smaller pores between every two ribs in the lower half (in three tiers); therefore, together, thirty-six thoracic meshes. Mouth strongly constricted, smooth, only one-third as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax, 0.11 long, 0.1 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Sethamphora enneapleura, n. sp.

Shell subovate, smooth, with slight collar stricture. Length of the two joints = 3 : 9, breadth = 4 : 8. Cephalis large, hemispherical, free, with small circular pores. Thorax inflated, ovate, with nine strong curved ribs, which are connected by five transverse circular rings at equal distances. Forty-five rounded, squarish, large meshes between them, in five transverse and nine longitudinal rows. Mouth constricted, smooth, half as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.08 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Sethamphora dodecapleura, n. sp.

Shell urceolate, smooth, with sharp collar stricture. Length of the two joints = 3 : 9, breadth = 5 : 9. Cephalis flat, cap-shaped, free, with twelve ribs, and very small pores between them. Thorax thick-walled, inflated, with subcylindrical cavity, and twelve prominent sharp ribs, alternating with twelve longitudinal rows of very small circular pores (eight pores in each row). Mouth constricted, half as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.09 long, 0.09 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

4. Sethamphora mongolfieri, Haeckel.

Eucyrtidium mongolfieri, Ehrenberg, 1854, Mikrogeol., Taf. xxxiv. fig. 18; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 72, Taf. x. fig. 3.

Shell urceolate, smooth, with distinct collar stricture. Length of the two joints = 2 : 9, breadth = 3 : 7. Cephalis campanulate, with eighteen ribs and small pores. Thorax nearly ellipsoidal, with eighteen prominent ribs, and eighteen longitudinal rows of regular circular pores between them (eight pores in each row; therefore 144 pores altogether). Mouth constricted, only one-third as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Fossil in Barbados.

5. Sethamphora costata, n. sp. Pl. [62], fig. 3.

Shell urceolate, smooth, very similar to the preceding species; also with eighteen longitudinal ribs, but differing in the larger size of the cephalis and its pores, and in the more slender and ovate form of the thorax. Length of the two joints = 5 : 10, breadth = 5 : 8. Pores of the cephalis more numerous. Mouth half as broad as the thorax.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.1 long, 0.08 broad.

Habitat.—Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.

6. Sethamphora serrata, n. sp.

Shell ovate, spinulate, without external collar stricture. Length of the two joints = 1 : 6, breadth = 2 : 4. Cephalis flat, cap-shaped, with small circular pores. Thorax ovate, truncate, with eighteen serrate longitudinal ribs, alternating with eighteen longitudinal rows of short and broad rather oblong pores (twenty to thirty pores in each row). Mouth strongly constricted, only one-fourth as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

7. Sethamphora ampulla, Haeckel.

Eucyrtidium ampulla, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 15; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 72, Taf. x. figs. 11, 12.

Shell broad, urceolate, spiny, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subspherical, with few small pores (in figs. 12a and 12b of Ehrenberg, loc. cit., broken off, so that the four pores of the cortinar septum appear). Thorax inflated, bottle-shaped, with twenty prominent, sharply dentate ribs, alternating with twenty longitudinal rows of circular pores (about eight pores in each row). Mouth flat, constricted, one-third as broad as the thorax.

Dimensions.—Cephalis 0.025 long, 0.03 broad; thorax 0.1 long, 0.14 broad.

Habitat.—Fossil in Barbados.

8. Sethamphora aërostatica, Haeckel.

Podocyrtis aërostatica, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xvi. fig. 4.

Shell broad, urceolate, smooth, with sharp collar stricture. Length of the two joints = 2 : 6, breadth = 3 : 8. Cephalis hemispherical, large, with few pores (broken off in fig. 4a of Ehrenberg, so that the six collar pores appear). Thorax inflated, bottle-shaped, with twenty-two to twenty-four smooth prominent ribs, alternating with the some number of longitudinal rows of small circular pores. Mouth very small, strongly constricted, scarcely as broad as the cephalis, with three short teeth.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Cryptocephalus, Haeckel, 1881, Prodromus, p. 430.

Definition.—Cephalis more or less hidden in thorax, being partly enveloped by its uppermost part.

9. Sethamphora microstoma, n. sp. (Pl. [57], fig. 5).

Cryptoprora microstoma, Haeckel, Atlas, pl. lvii., fig. 5.

Shell ovate, smooth, without external collar stricture. Length of the two joints = 1 : 6, breadth = 2 : 4. Cephalis flat, cap-shaped, without ribs, with small circular pores. Thorax ovate, with twenty-four prominent ribs, alternating with deep longitudinal furrows, each of which contains a series of about fifteen small circular pores. Mouth very small, representing a short cylindrical tube, which is only one-eighth as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

Habitat.—Western Tropical Pacific, Station 220, depth 1100 fathoms.

10. Sethamphora favosa, n. sp, (Pl. [57], fig. 4).

Cryptocephalus favosus, Haeckel, 1881, Prodromus, p. 430.

Shell ovate, dimply. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, small, completely hidden in the thickened top of the thorax (but very distinct in the longitudinal section). Thorax ovate, with twenty-five to thirty longitudinal ribs, alternating with the same number of longitudinal furrows, each of which contains ten to twelve circular, hexagonally framed pores. In the smooth wall of the peristome only twelve triangular ribs are visible. Mouth constricted, one-third as broad as the thorax.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.09 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 560. Sethopyramis,[[177]] Haeckel, 1881, Prodromus, p. 432 (sensu emendato !)

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network simple. Cephalis commonly without horn.

The genus Sethopyramis and the four following genera form together a peculiar small group (Sethopyramida), characterised by the slender pyramidal shell, in the wall of which numerous (six to nine or more) radial ribs are enclosed. These ribs may be regarded as the terminal feet of a Calpophæna or Halicalyptra, which become connected by transverse bars. Sethopyramis may be derived also directly from Patagospyris by loss of the primary sagittal ring and reduction of the cephalis.

Subgenus 1. Sestropyramis, Haeckel.

Definition.—Pyramidal shell with six radial main beams (sometimes also five or seven, as individual varieties).

1. Sethopyramis scalaris, Haeckel.

Cornutella scalaris, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 1.

Shell smooth, slenderly pyramidal, hexagonal. Cephalis large, subglobular, hyaline, without pores (or with very small and scarce pores). Thorax with six straight (or little curved) stout longitudinal ribs or radial beams, which are connected by twenty to thirty complete, hexagonal, horizontal rings. The large meshes so produced are regular, square, their length and breadth equally and gradually increasing towards the mouth.

Dimensions.—Cephalis 0.04 diameter; thorax (with twenty-four transverse rings) 0.4 long, 0.15 broad at the mouth.

Habitat.—Fossil in Barbados.

2. Sethopyramis hexalactis, n. sp.

Shell thorny, of the same form as, and similar structure to, the preceding species, but differing in the spiny surface and the smaller subglobular cephalis, which bears small circular pores and an oblique conical horn twice the length. The whole surface is covered with short conical thorns.

Dimensions.—Cephalis 0.02 diameter; thorax (with twenty transverse rings) 0.25 long, 0.1 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Subgenus 2. Cephalopyramis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Pyramidal shell with nine radial main beams (sometimes also eight or ten, as individual varieties).

3. Sethopyramis enneactis, n. sp. (Pl. [56], fig. 7).

Cephalopyramis enneactis, Haeckel, 1881, Prodromus et Atlas, pl. lvi. fig. 7.

Shell smooth, slender, pyramidal. Cephalis large, ovate, with pointed apex, nearly hyaline, with very few and small scattered pores. Thorax very slenderly pyramidal, with straight lateral outlines, and nine stout and straight radial beams, which are connected by fifteen to twenty horizontal complete rings. Meshes subregular, square, simple, without secondary network; their length and breadth equally increasing towards the mouth.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax (with twenty transverse rings) 0.24 long, 0.1 broad at the mouth.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.

4. Sethopyramis quadrata, n. sp. (Pl. [54], fig. 2).

Shell smooth, slenderly pyramidal, very similar in form and structure to the preceding species; differing from it in the rudimentary cephalis, which is very small, hemispherical, with few small porules. The three internal cortinar bars of the collar stricture are present; when they become lost this species passes over into Bathropyramis quadrata (Pl. [54], fig. 1).

Dimensions.—Cephalis 0.01 long, 0.02 broad; thorax (with ten transverse rings) 0.15 long, 0.1 broad at the mouth.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Sethopyramis quadratella, Haeckel.

Cornutella quadratella, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 2.

Litharachnium quadratella, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol, xxxvi. p. 540, Taf. xxxiii. fig. 37.

Shell smooth, broadly pyramidal. Cephalis ovate, small, blunt, hyaline, with very few and small pores (in the figure of Ehrenberg broken off). Thorax broadly pyramidal, with straight lateral outlines, and nine stout and straight radial beams, which are connected by eight to twelve horizontal complete rings. Meshes in the upper half regular, square, in the lower half broad, rectangular (in the tenth transverse row twice as broad as long).

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax (with ten transverse rings) 0.15 long, 0.15 broad.

Habitat.—Fossil in Barbados.

6. Sethopyramis trapezoides, n. sp.

Shell smooth, broadly pyramidal. Cephalis large, ovate, hyaline, without pores; its collar septum exhibits distinctly the four collar pores (two larger cardinal and two smaller jugular pores). Thorax broad, pyramidal, with slightly concave lateral outlines and nine (sometimes eight or ten) curved ribs, which are connected by eighteen to twenty-four complete transverse rings. The large meshes, so produced, have the form of a parallel trapezoid, and are in the eighth transverse row three times as broad as long. (Differs from Bathropyramis trapezoides, Pl. [54], fig. 3, mainly by the possession of a well developed cephalis).

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax (with eighteen rings) 0.32 long, 0.24 broad.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

7. Sethopyramis spinosa, n. sp.

Shell thorny, slender, pyramidal. Cephalis small, subspherical, with few small pores and a straight, vertical, conical horn twice the length. Thorax with nine straight ribs, which are connected by sixteen to twenty complete transverse nine-angled rings. The large meshes so produced are subregular, square. From each nodal point a short conical spine arises. (Differs from the similar Bathropyramis spinosa, Pl. [54], fig. 4, by the development of the cephalis and the simple pointed, unforked spines.)

Dimensions.—Cephalis 0.03 diameter; thorax (with sixteen rings) 0.2 long, 0.12 broad.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

8. Sethopyramis hexagonalis, n. sp.

Shell papillate, slender, pyramidal. Cephalis small, hemispherical, with a straight conical horn twice the length, and small circular pores. Thorax conical, with slightly convex outlines and nine stout, somewhat curved ribs in zig-zag form, which are connected by ten to twelve interrupted transverse bars. From each nodal point a small conical papilla arises. The large meshes so produced are regular, hexagonal, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.03 diameter; thorax (with twelve transverse rows of meshes) 0.18 long, 0.12 broad.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

9. Sethopyramis cyclomma, n. sp.

Shell thorny, slender, pyramidal. Cephalis large, subspherical, with numerous very small circular pores, and a small conical horn of the same length. Thorax similar in form and structure to that of the preceding species; but each hexagonal mesh is provided with a very thin circular hyaline ring (like a diaphragm), so that the openings are not hexagonal, but circular. From each nodal point a short pointed conical or slightly forked spine arises.

Dimensions.—Cephalis 0.02 diameter; thorax (with ten transverse rows of meshes) 0.18 long, 0.14 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Subgenus 3. Actinopyramis, Haeckel.

Definition.—Pyramidal shell with twelve or more radial beams (commonly twelve to twenty-four, sometimes forty or more).

10. Sethopyramis dodecalactis, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, hyaline, with a short conical horn. Thorax with twelve radial ribs in the upper half, between which twelve others are interpolated in the lower half. These are connected by twenty to twenty-four complete transverse rings. The meshes so produced are subregular, rectangular.

Dimensions.—Cephalis 0.03 diameter; thorax 0.6 long, 0.2 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

11. Sethopyramis bicornis, n. sp.

Shell spiny, slender, pyramidal. Cephalis small, spherical, hyaline, with two divergent conical horns, the major (occipital) three times and the minor (frontal) twice as long. Thorax slender, pyramidal, campanulate, thorny, with twenty to thirty radial beams, which are little curved, convex in the upper, concave in the lower half, and connected by numerous interrupted transverse bars. Meshes in the upper third rounded, in the lower two-thirds quadrangular, of very different sizes. Surface covered with spinules.

Dimensions.—Cephalis 0.02 diameter; thorns 0.9 long, 0.4 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

12. Sethopyramis maxima, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, with few small pores, and a stout, vertical, conical horn twice the length. Thorax very prolonged, conical, with straight lateral outlines and numerous (twenty to fifty) radial beams (in the upper third twelve, in the middle third twenty-four, in the lower third forty to fifty, by interpolation); they are connected by very numerous interrupted transverse bars. Meshes subregular, quadrangular. Surface smooth.

Dimensions.—Cephalis 0.02 diameter; thorax 1.05 long, 0.45 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 561. Plectopyramis,[[178]] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network double, the large primary meshes being fenestrated by fine secondary network. Cephalis commonly without horn.

The genus Plectopyramis differs from the preceding Sethopyramis, its ancestral form, only in the peculiar double fenestration of the shell, the large primary meshes of which are separated by strong bars, and filled up by a very delicate arachnoidal network, composed of small pores and very thin threads between them. This double lattice-work often exhibits a very remarkable regularity. As in the preceding genus, the number of radial ribs is commonly six or nine, rarely twelve to twenty or more.

Subgenus 1. Hexapleuris, Haeckel.

Definition.—Pyramidal shell with six radial main beams (sometimes five or seven in individual varieties).

1. Plectopyramis magnifica, Haeckel.

Polycystina magnifica, Bury, 1862, Polycystins of Barbados, pl. xi. fig.

Shell smooth, slender, pyramidal. Cephalis large, ovate, pointed, separated from the thorax by a very deep collar stricture, with few irregular pores. Thorax with six strong and straight radial beams, which are connected by about twenty horizontal, hexagonal rings. The large meshes so produced are regular, square, and filled up by an extremely delicate secondary arachnoidal network, composed of regular square pores (as in Pl. [54], figs. 7, 8).

Dimensions.—Cephalis 0.06 long, 0.04 broad; thorax (with twenty transverse rings) 0.4 long, 0.12 broad.

Habitat.—Fossil in Barbados.

2. Plectopyramis hexapleura, n. sp.

Shell thorny, slender, pyramidal. Cephalis large, ovate, blunt, with deep collar stricture. Thorax with six strong and straight radial beams, which are connected by numerous (twenty to thirty) interrupted transverse bars. The large meshes so produced are irregular, quadrangular, and filled up by irregular, delicate, secondary network, with small polygonal pores.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax 0.3 long, 0.1 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

Subgenus 2. Enneapleuris, Haeckel.

Definition.—Pyramidal shell with nine radial main beams (sometimes eight or ten in individual varieties).

3. Plectopyramis dodecomma, n. sp. (Pl. [54], fig. 6).

Shell smooth, slenderly pyramidal, with straight outlines. Cephalis conical, obtuse, with thirty-six small square pores (in nine divergent longitudinal rows, each of four pores). Collar septum (between cephalis and thorax) with four distinct collar pores. Thorax pyramidal, with nine very stout and straight angular radial beams, which are connected by ten to fifteen broad horizontal nine-angled rings. Each of the large regular, square meshes so produced contains a very delicate fenestration, with twelve regular, square pores, separated by two transverse and three longitudinal crossed threads. A very regular and remarkable structure.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax (with ten rings) 0.2 long, 0.15 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

4. Plectopyramis quadratomma, n. sp.

Shell smooth, slenderly pyramidal. Cephalis large, ovate, hyaline, with few very small basal pores and deep collar stricture. Thorax pyramidal, with straight outline, and nine very stout and straight radial beams, which are connected by fifteen to twenty horizontal nine-angled rings. Each of the large regular, square meshes so produced is filled up by a very delicate arachnoidal network, with very numerous and small square pores (as in the similar Cinclopyramis infundibulum, Pl. [54], fig. 7, which differs in the loss of the cephalis).

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax (with fifteen rings) 0.32 long, 0.2 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Plectopyramis trapezomma, n. sp. (Pl. [54], fig. 8).

Shell smooth, broadly pyramidal, with concave lateral outlines. Cephalis hemispherical, small, with numerous small, circular pores. Thorax pyramidal, with nine stout, concavely curved radial beams, which are connected by twelve to sixteen horizontal nine-angled rings. The large meshes so produced are in the upper half square, in the lower half parallel trapezoid (in the fifteenth ring three times as broad as long), and filled up by a secondary arachnoidal network, with very numerous and small square pores.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax (with fifteen rings) 0.22 long, 0.2 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

6. Plectopyramis polygonomma, n. sp.

Shell smooth, pyramidal, very similar to the preceding species; differing from it in the irregular shape of the delicate polygonal (not tetragonal) secondary network, filling up the large rectangular meshes. The cephalis is larger, hyaline, pear-shaped, pointed, without pores, with a deep collar stricture. The nine radial beams of the thorax are less concave.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax (with fifteen rings) 0.3 long, 0.22 broad.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

7. Plectopyramis heteromma, n. sp.

Shell smooth, slenderly pyramidal, with concave outlines. Cephalis very small, subspherical, with a small oblique, conical horn, and very small, scarce circular pores. Thorax with nine stout concavely curved radial beams, which are connected by numerous (thirty to fifty or more) interrupted transverse bars. The large irregular meshes so produced are filled up by irregular, polygonal, delicate lattice-work.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.6 long, 0.3 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

8. Plectopyramis serrata, n. sp.

Shell thorny, slenderly pyramidal, with straight outlines. Cephalis very small, spherical, with a long oblique, conical horn, and very small circular pores. Thorax with nine stout, straight, regularly serrate ribs or radial beams, which are connected by numerous (twenty to thirty or more) interrupted transverse bars. The latter, being crossed by intercalated and interrupted irregular radial beams, produce a subregular secondary network of rectangular meshes of different sizes.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax, 0.3 long, 0.2 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

9. Plectopyramis fenestrata, Haeckel.

Pyramis fenestrata, Bury, 1862, Polycystins of Barbados, pl. xxi. fig. 8.

Shell thorny, broadly pyramidal, with straight outlines. Cephalis very small, spherical, hyaline. Thorax with nine stout, spinulate, straight ribs or radial beams, which are connected by ten to fifteen transverse bars, which in the upper half are complete rings, in the lower half interrupted, and crossed by irregularly intercalated radial beams. Meshes therefore irregular, quadrangular. All the bars are thorny.

Dimensions.—Cephalis 0.01 diameter; thorax 0.2 long, 0.16 broad.

Habitat.—Tropical Atlantic.

10. Plectopyramis furcata, n. sp.

Shell spiny, slenderly pyramidal, with straight outlines. Cephalis small, spherical, with few small pores. Thorax with nine stout and straight spinulate ribs, which are connected by a variable number of irregular interrupted transverse bars; the large quadrangular meshes so produced are filled up by irregular delicate network. The entire surface of the thorax is covered with short forked spines.

Dimensions.—Cephalis 0.02 diameter; thorax 0.3 long, 0.2 broad.

Habitat.—Indian Ocean (Zanzibar), Pullen, depth 2200 fathoms.

Subgenus 3. Polypleuris, Haeckel.

Definition.—Pyramidal shell with numerous (twelve or more) radial main beams (commonly twelve to eighteen, sometimes twenty to thirty or more).

11. Plectopyramis polypleura, n. sp. (Pl. [56], fig. 8).

Shell smooth, slenderly conical, with straight outlines. Cephalis small, subspherical, with very small dot-like pores, and an oblique conical horn twice the length. Thorax with numerous (twenty to thirty) divergent longitudinal ribs; usually twelve of these radial beams appear as stronger, primary main ribs, and twelve to eighteen other as secondary, feebler, interpolated ribs. They are crossed by numerous (twenty to forty or more) horizontal rings. The large meshes so produced are quadrangular, and partly filled up by a very delicate secondary network, with small square pores.

Dimensions.—Cephalis 0.03 diameter; thorax 0.36 long, 0.24 broad.

Habitat.—Central Pacific, Station 267, depth 2700 fathoms.

12. Plectopyramis lagena, n. sp.

Shell smooth, wine-bottle shaped, or slenderly conical-campanulate, with bent outlines, which are concave in the upper, convex in the lower half. Cephalis very small, spherical, hyaline, without pores. Thorax with twenty-four radial ribs, twelve stronger primary, alternating with twelve feebler secondary. They are crossed by interrupted transverse bars. The irregular quadrangular meshes so produced are filled up by a delicate, irregular, secondary network.

Dimensions.—Cephalis 0.02 diameter; thorax 0.5 long, 0.3 broad.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

Genus 562. Spongopyramis,[[179]] n. sp.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network spongy. Cephalis commonly without horn.

The genus Spongopyramis has arisen from Sethopyramis by development of an irregular spongy framework around the lattice-shell, and is one of the small number of Cyrtoidea in which the shell-wall exhibits a spongy structure. In both observed species the cephalis is small, but evident.

1. Spongopyramis spongiosa, n. sp. (Pl. [56], fig. 10).

Plectopyramis spongiosa, Haeckel, 1881, Prodromus et Atlas, loc. cit.

Shell partly or entirely enveloped by spongy framework, slender, pyramidal, with rather straight outlines. Cephalis very small, ovate, hyaline. Thorax with nine very stout and nearly straight ribs, which are connected by fifteen to twenty or more irregular, interrupted transverse bars. The irregular quadrangular meshes so produced are filled up by an irregular secondary network, with meshes of very different size and form. The dense spongy envelope, which in the specimen figured covered only half the shell, was complete in another older specimen.

Dimensions.—Cephalis 0.015 long, 0.01 broad; thorax 0.4 long, 0.25 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Spongopyramis spongoplecta, n. sp.

Shell entirely enveloped by spongy framework, pyramidal, with straight outlines. Cephalis ovate (twice as large as in the preceding species), with small circular pores. Thorax with twelve stout and straight ribs, which are connected by twenty to twenty-five annular, transverse bars. The subregular square meshes so produced are filled up by irregular, spongy network, which envelops the whole shell more loosely than in Spongopyramis spongiosa.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.5 long, 0.2 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 563. Acanthocorys,[[180]] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the pyramidal thorax, prolonged into divergent terminal feet. Network simple. Cephalis commonly with several horns.

The genus Acanthocorys and the following nearly allied Arachnocorys possess a near relation to the three preceding pyramidal genera, but differ from them in the terminal prolongation of the radial ribs, which are commonly spiny and form a corona of free feet around the mouth of the thorax. The cephalis is usually much larger than in the three preceding genera, and bears a variable number of radial horns. Therefore these two genera are probably older and nearer to the common ancestral form of the Sethophormida than the preceding genera. It may be derived directly from Dictyophimus by interpolation of three secondary (interradial) ribs between the three primary (perradial) ribs.

Subgenus 1. Acanthocorallium, Haeckel.

Definition.—Thorax with six divergent ribs or radial beams (three primary or perradial alternating with three secondary or interradial).

1. Acanthocorys hexapodia, n. sp.

Cephalis large, ovate, with subregular hexagonal pores, and six strong, conical, simple, divergent horns of the same length. Thorax flat, conical, smooth, with six large triangular basal holes, separated by six strong, prismatic, smooth beams, which are connected only near the distal end by a hexagonal ring of delicate, irregular network. Collar septum with three meshes, separated by the three centripetal prolongations of the three primary ribs.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.12 long, 0.24 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

2. Acanthocorys pristipodia, n. sp.

Cephalis large, hemispherical, with irregular, polygonal pores, and numerous (ten to twenty) bristle-shaped, radiating horns, which are conical at the base, and twice as long. Thorax flatly campanulate, thorny, with six strong, serrate or spinulate, divergent, radial ribs, prolonged into six free conical feet of the same length. Meshes of the thorax irregular, polygonal, a corona of six larger ones at the base. Collar septum with four meshes, shaped as in Pl. [56], fig. 6.

Dimensions.—Cephalis 0.04 long, 0.06 broad; thorax 0.08 long, 0.18 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Acanthocorys macropodia, n. sp.

Cephalis small, subspherical, with irregular, roundish pores and numerous small, bristle-shaped horns. Length of the two joints = 1 : 2, breadth = 1 : 6. Thorax sexangular, pyramidal, with six very long and straight, widely divergent feet, which are prismatic and spiny, and three to five times as long as the breadth of the shell. Only the upper third of the six ribs is connected by irregular, roundish network, with six large triangular holes at the base. Collar septum with four meshes which have the same relation to the six ribs as in Sethophormis hexalactis (Pl. [56], fig. 6).

Dimensions.—Cephalis 0.025 diameter, thorax 0.05 long, 0.15 broad.

Habitat.—Central Pacific, Station 271, surface.

4. Acanthocorys bütschlii, Haeckel.

? Clathrocanium ehrenbergii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 514, 539, Taf. xxxii. fig. 18, a, b.

Cephalis large, subspherical, with numerous small, circular pores and three to six divergent, slender, apical horns. Thorax flatly conical, smooth, not much larger than the cephalis, with six large, triangular or ovate basal holes between the six ribs. Three of these ribs are primary or perradial, and arise immediately from the collar septum, alternating with three secondary or interradial ribs, which arise more outside. The specimen observed by me exhibited six apical horns, and was more complete than that figured by Bütschli, the six ribs being prolonged over the connecting lattice-girdle into six short, divergent feet.

Dimensions.—Cephalis 0.06 long, 0.06 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Acanthocoronium, Haeckel.

Definition.—Thorax with nine divergent ribs or radial beams, three of which are primary or perradial, the other six secondary or interradial.

5. Acanthocorys umbellifera, Haeckel.

Arachnocorys umbellifera, Haeckel, 1862, Monogr. d. Radiol., p. 305, Taf. vi. fig. 12.

Cephalis large, ovate, with subregular, circular pores and numerous divergent, simple spines of different lengths. Thorax flatly conical, with nine strong, divergent ribs, which in the distal half are free, in the proximal half connected by numerous transverse beams, forming irregular polygonal meshes. Dorsal face of the thorax armed with scattered ascending spines.

Dimensions.—Cephalis 0.05 long, 0.035 broad; thorax 0.05 long, 0.12 broad.

Habitat.—Mediterranean (Messina); Atlantic, Station 354, surface.

6. Acanthocorys triloba, n. sp.

Cephalis large, campanulate, trilobed, with irregular, roundish pores, numerous spines, and a large pyramidal horn on the top, which is connected by three constricted arches with the base of the horizontal collar beams. From the latter arise as centrifugal prolongations three stout, curved, primary ribs of the flatly vaulted thorax, and each of these gives off at the base two opposite, lateral, secondary ribs. These nine ribs are spiny, and connected by irregular, arachnoidal network.

Dimensions.—Cephalis 0.05 long, 0.07 broad; thorax 0.08 long, 0.18 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

7. Acanthocorys enneapodia, n. sp.

Cephalis large, ovate, with irregular roundish pores, and numerous divergent, ascending spines. Thorax smooth, conical, little larger, with the same network, and nine larger, triangular holes at the base; with nine straight, equally-disposed ribs, which are prolonged into slender feet twice the length. With these latter alternate nine shorter radial spines, arising from the truncate peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.05 long, 0.09 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

8. Acanthocorys macroceras, n. sp. (Pl. [97], fig. 12).

Cephalis large, hemispherical, spiny, with regular, circular pores, and a very large, cylindrical, vertical horn five times as long as the whole shell. Thorax spiny, campanulate, with irregular, roundish pores and nine strong, curved ribs, prolonged into nine slender, divergent feet twice the length, which are curved, convex in the proximal half and concave in the distal half.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.12 long, 0.2 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

9. Acanthocorys furcata, n. sp.

Cephalis large, subspherical, spiny, with irregular, roundish pores. Thorax flatly conical, thorny, with irregular, polygonal pores, decreasing in size toward the mouth, and with nine straight divergent ribs, which at the peristome are forked and prolonged into eighteen slender, very long, bristle-shaped feet.

Dimensions.—Cephalis 0.045 diameter, thorax 0.07 long, 0.13 broad.

Habitat.—South Atlantic, Station 323, depth 1900 fathoms.

Subgenus 3. Acanthocorythium, Haeckel.

Definition.—Thorax with a variable number (ten to twenty or more) radial ribs, prolonged into free terminal feet.

10. Acanthocorys dodecaster, n. sp.

Cephalis small, subspherical, with small circular pores and a large conical horn of twice the length, and some accessory spines. Thorax thorny, flatly campanulate, with twelve stout curved ribs, which at the peristome are prolonged into twelve slender, curved feet of twice the length; four of them are centrifugal prolongations of the four cortinar beams separating the four large meshes of the collar septum; eight other ribs are secondary, interpolated in pairs between the former. At the base of the thorax are twelve large triangular holes between the ribs; the other network is irregular, with polygonal meshes.

Dimensions.—Cephalis 0.03 diameter, thorax 0.05 long, 0.12 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

11. Acanthocorys polypodia, n. sp.

Cephalis small, hemispherical, with small, roundish pores and divergent radial spines. Thorax flatly conical, spiny, with twenty to twenty-four divergent, straight ribs, which in the proximal third are separated by the same number of large, triangular meshes, in the middle third connected by irregular network, in the distal third free.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.15 broad.

Habitat.—Central Pacific, Station 273, depth 2350 fathoms.

Genus 564. Arachnocorys,[[181]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 837.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the pyramidal thorax, prolonged into divergent terminal feet. Network double, with an arachnoidal outer mantle around the inner lattice-shell. Cephalis commonly with numerous horns.

The genus Arachnocorys has been derived from the preceding Acanthocorys, by development of numerous external siliceous threads which connect the radial horns of the cephalis with the secondary spines arising from the thoracic ribs. In this way there becomes formed an outer arachnoidal framework, enveloping loosely, like a delicate mantle, the inner primary lattice-shell.

Subgenus 1. Arachnocorallium, Haeckel.

Definition.—Thorax with six divergent ribs or radial beams (three primary or perradial, alternating with three secondary or interradial).

1. Arachnocorys hexaptera, n. sp.

Arachnocorys circumtexta (juv.?), R. Hertwig, 1879, Organism. d. Radiol., p. 79, Taf. viii. fig. 2a.

Cephalis large, subspherical, with irregular, polygonal pores, and numerous bristle-shaped spines twice the length; on the centre of the top a single larger vertical horn. Thorax flatly conical, with six strong and straight widely divergent ribs, which in the proximal half are separated by six large holes, in the distal half connected by a broad ring of irregular network. From each rib arises a perpendicular branch, and these branches are connected together, and with the spines of the cephalis, by arachnoidal network.

Dimensions.—Cephalis 0.04 diameter, thorax 0.08 long, 0.24 broad.

Habitat.—Central Pacific, Station 266; Mediterranean, surface.

2. Arachnocorys discoides, n. sp.

Cephalis small, pyramidal, with irregular, roundish pores and numerous thin spines, on the top a single larger vertical horn. Thorax very flat, nearly discoidal, with six strong and straight ribs, which by communication of few larger and numerous smaller branches form an irregular network with polygonal meshes. From each of the six ribs arise two or three larger, perpendicular branches of half the length, and from the network numerous smaller spines. All these dorsal spines of the shell are connected by a dense arachnoidal wicker-work.

Dimensions.—Cephalis 0.02 diameter, thorax 0.04 long, 0.3 broad.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 2. Arachnocoronium, Haeckel.

Definition.—Thorax with nine divergent ribs or radial beams, three of which are primary or perradial, the other six secondary or interradial. (Sometimes eight or ten occur instead of the nine normal ribs.)

3. Arachnocorys circumtexta, Haeckel.

Arachnocorys circumtexta, Haeckel, 1862, Monogr. d. Radiol., p. 304, Taf. vi. figs. 9-11.

Arachnocorys circumtexta, R. Hertwig, 1879, Organism. d. Radiol., p. 78, Taf. viii. fig. 2.

Cephalis large, subspherical, with numerous roundish pores, and eight to ten slender, conical horns twice the length. Thorax flatly conical, with nine strong, straight, widely divergent, conical feet, each of which bears in the middle of its outer side a perpendicular ascending branch of half the length. These branches and the horns of the cephalis are connected by very thin, parallel, arachnoidal threads. Network of the thorax irregular, with nine larger triangular holes at the base. Collar septum with numerous, irregular, roundish pores.

Dimensions.—Cephalis 0.04 to 0.05 diameter, thorax 0.08 to 0.12 long, 0.15 to 0.25 broad.

Habitat.—Mediterranean (Messina); Atlantic, Stations 347 to 354, surface.

4. Arachnocorys enneaptera, n. sp.

Cephalis large, campanulate, with irregular, polygonal pores, two larger stout pyramidal and numerous slender, bristle-shaped horns. Thorax of the same structure as in the preceding species, only the nine basal holes are of twice the size; the lower network denser (as in Clathrocanium diadema, Pl. [64], fig. 2). Collar septum with numerous, irregular, roundish pores.

Dimensions.—Cephalis 0.05 diameter, thorax 0.12 long, 0.22 broad.

Habitat.—Tropical Atlantic, Station 338, surface.

5. Arachnocorys araneosa, n. sp. (Pl. [56], fig. 11).

Cephalis large, subspherical, with circular, subregular, hexagonally framed pores, and twenty to thirty slender, cylindrical, straight radial spines. Thorax flatly conical, nearly of the same shape as in the two preceding species, but with nine longer ribs, and more irregular, broader network between them. From the middle of each rib arises, nearly horizontally, a strong branch, which is directed outwards. These branches are connected with the spines of the cephalis as well as with the distal half of the ribs, by dense and delicate arachnoidal network, composed of parallel, very thin, siliceous threads (in fig. 11 only partially represented). Collar septum with numerous irregular, roundish pores.

Dimensions.—Cephalis 0.04 diameter, thorax 0.1 long, 0.2 broad.

Habitat.—Central Pacific, Station 270 to 274, surface.

6. Arachnocorys arachnodiscus, n. sp.

Cephalis small, campanulate, conical, with a single very large conical central horn, and numerous smaller accessory spines. Thorax in form and structure similar to that of the three preceding species, but much flatter, being nearly discoidal. The meshes of the network are smaller and more numerous, irregularly polygonal, and the nine basal holes little larger. Collar septum with four large meshes (as in Pl. [60], fig. 6).

Dimensions.—Cephalis 0.25 long, 0.3 broad; thorax 0.04 long, 0.24 broad.

Habitat.—North Pacific, Station 248, surface.

7. Arachnocorys trifida, n. sp.

Cephalis large, campanulate, with irregular, roundish pores and numerous ramified spines; in the centre of the top a larger pyramidal oblique horn of twice the length. Thorax cap-shaped, flatly vaulted, with nine strong convex ribs, prolonged into slender free feet. Three of these nine ribs are the centrifugal prolongations of the three cortinar bars (united in the centre of the collar stricture, separating its three large cortinar meshes); the other six are diverging lateral branches of the former, arising in pairs at both sides of its base. All nine ribs are connected by delicate arachnoidal network with irregular polygonal meshes. From its surface arise thin bristles, and from the base of each main rib a stout, perpendicular branch. All these dorsal spines are connected by irregular, arachnoidal wicker-work, covering thorax and cephalis. (A remarkable primitive species?)

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.07 long, 0.18 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Subgenus 3. Arachnocorythium, Haeckel.

Definition.—Thorax with a variable number of radial ribs (twelve to twenty or more), prolonged into free terminal feet.

8. Arachnocorys polyptera, n. sp.

Cephalis large, subspherical, with irregular, roundish pores and numerous radial spines. Thorax flatly conical, with numerous radial ribs (twenty to thirty), which are in the distal half free, in the proximal half connected by delicate arachnoidal wicker-work, with polygonal, irregular meshes. From its dorsal face arise numerous radial spines, which are connected together, and with the cephalic spines, by very thin and numerous threads, parallel between every two spines. Similar to Arachnocorys araneosa (Pl. [56], fig. 11), but differing in the structure of the cephalis, and in the greater number of the ribs and spines.

Dimensions.—Cephalis 0.04 diameter, thorax 0.12 long, 0.24 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Genus 565. Anthocyrtoma,[[182]] n. gen.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with six terminal feet around the mouth. Cephalis free, with an apical horn.

The genus Anthocyrtoma and the four following genera form together the peculiar group of Carpocanida, comprising all those Sethophormida in which the original thoracic ribs are lost, and only the terminal feet remain. Anthocyrtoma is the simplest form of this group, possessing only six terminal feet, three primary perradial, and three alternating, secondary, interradial. It may be directly derived either from Lychnocanium, by interpolation of three interradial feet, or from Hexaspyris by loss of the sagittal ring.

1. Anthocyrtoma serrulata, Haeckel.

Anthocyrtis serrulata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. vi. fig. 7.

Shell pear-shaped, rough, with obliterated collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis ovate, with very small pores, and a stout conical horn of the same length. Abdomen inflated, truncate, with larger, regular, circular pores, twice as broad as the constricted mouth. Six feet vertical, parallel, serrate, all of the same size, about as long as the cephalis.

Dimensions.—Cephalis 0.06 long, 0.05 broad; thorax 0.2 long, 0.17 broad.

Habitat.—Fossil in Barbados.

2. Anthocyrtoma alterna, n. sp.

Shell pear-shaped, smooth, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis hemispherical, with a slender conical horn of twice the length. Abdomen inflated, subglobular, with regular, circular, hexagonally framed pores, three times as broad as the narrow, constricted mouth. Six feet conical, smooth, somewhat divergent, alternating, of different sizes; the three larger (perradial) half as long as the shell, and twice as long as the three smaller (interradial). (Similar to Anthocyrtis ventricosa.)

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.15 long, 0.18 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 566. Anthocyrtis,[[183]] Ehrenberg, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1847, p. 54.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with nine terminal feet around the mouth. Cephalis free, with an apical horn.

The genus Anthocyrtis (in the original definition of Ehrenberg) contained all Dicyrtida without thoracic ribs, with terminal feet. We here restrict the definition to those Sethophormida in which the number of free terminal feet is constantly nine (three primary perradial and three alternate pairs of secondary interradial feet). Anthocyrtis may be derived either directly from Patagospyris by loss of the sagittal ring, or from Lychnocanium by interpolation of three secondary feet.

Subgenus 1. Anthocyrtella, Haeckel.

Definition.—Feet of the peristome-corona divergent, their basal distance less than their terminal distance.

1. Anthocyrtis mespilus, Ehrenberg.

Anthocyrtis mespilus, Ehrenberg, 1854, Taf. xxxvi. fig. 13; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 66, Taf. vi. fig. 4 (not 5).

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 6. Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax nearly hemispherical, with regular, circular, quincuncial pores. Mouth scarcely constricted, with nine divergent, triangular, lamellar feet, about as long as the thorax.

Dimensions.—Cephalis 0.012 long, 0.02 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Fossil in Barbados.

2. Anthocyrtis furcata, Ehrenberg.

Anthocyrtis furcata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 2.

Shell smooth, with deep collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 6. Cephalis hemispherical, with a short pyramidal horn of half the length. Thorax hemispherical, with large, irregular, roundish pores. Mouth scarcely constricted, with nine divergent, curved, slender feet, which are about as long as the shell, and forked at the distal end.

Dimensions.—Cephalis 0.01 long, 0.02 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Fossil in Barbados.

3. Anthocyrtis butomus, n. sp.

Shell thorny, with obliterated collar stricture. Length of the two joints = 2 : 6, breadth = 2 : 7. Cephalis ovate, with very small and scarce pores, and a conical horn of the same length. Thorax inflated, pear-shaped, with regular, circular, quincuncial pores. Mouth about half as broad, constricted, with nine divergent, broad, nearly square, lamellar feet, half as long as the thorax (similar to Anthocyrtis serrulata, Ehrenberg, loc. cit., Taf. vi. fig. 7).

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.12 long, 0.14 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

4. Anthocyrtis ventricosa, Ehrenberg.

Anthocyrtis ventricosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. viii. fig. 1.

Shell thorny, with obliterated collar stricture. Length of the two joints = 1 : 7, breadth = 2 : 7. Cephalis hemispherical, hyaline, without pores, with a slender, conical horn, of about the same length. Thorax inflated, pear-shaped or subspherical, with regular, circular, quincuncial pores. Mouth only one-third as broad, much constricted, with nine divergent, slender, conical feet, about one-fifth as long as the diameter of the shell (partly broken off in Ehrenberg's figure).

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.14 long, 0.14 broad.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms; also fossil in Barbados.

Subgenus 2. Anthocyrtissa, Haeckel.

Definition.—Feet of the peristome-corona parallel, vertical; their basal and terminal distances equal.

5. Anthocyrtis ophirensis, Ehrenberg.

Anthocyrtis ophirensis, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. ix. fig. 13.

Shell smooth, with slight collar stricture. Length of the two joints = 2 : 4, breadth = 1 : 5. Cephalis ovate, with irregular, roundish pores, and a pyramidal, excentric, vertical horn of the same length. Thorax campanulate, with delicate network of large, regular, hexagonal pores. Mouth scarcely constricted, with nine parallel, vertical, conical feet, about as long as the cephalis. (In the specimen figured by Ehrenberg only seven feet are represented, two being broken off; two other specimens of this species, captured by Rabbe, exhibited nine regularly disposed feet.)

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Indian Ocean, Zanzibar (Pullen); Madagascar (Rabbe), surface.

6. Anthocyrtis lauranthus, n. sp.

Shell smooth with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis ovate, with large, roundish pores, and a conical horn of twice the length. Thorax inflated, campanulate, with regular, circular, hexagonally framed pores. Mouth two-thirds as broad, little constricted, with nine parallel, vertical, broad, lamellar, triangular feet, half as long as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Central Pacific, Station 266 to 270, depth 2550 to 2925 fathoms.

7. Anthocyrtis grossularia, Ehrenberg.

Anthocyrtis grossularia, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 6.

Shell spiny, with deep collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 4. Cephalis subspherical, thorny, with a conical horn of the same length. Thorax ovate, spiny, with numerous densely-crowded, subregular, circular pores. Mouth about half as broad, constricted, with nine parallel, vertical, slender, conical feet, about as long as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.2 long, 0.18 broad.

Habitat.—Fossil in Barbados.

8. Anthocyrtis subglobosa, n. sp.

Shell spiny, with deep collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 7. Cephalis subspherical, with a conical horn twice the length. Thorax nearly spherical, with small and very numerous, regular, circular pores. Mouth only one-third as broad, constricted, with nine parallel, vertical, square, lamellar feet, about twice as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.035 broad; thorax 0.2 long, 0.2 broad.

Habitat.—South Pacific, Station 297, depth 1775 fathoms.

Subgenus 3. Anthocyrtura, Haeckel.

Definition.—Feet of the peristome-corona convergent, their basal distance greater than their terminal distance.

9. Anthocyrtis enneaphylla, n. sp.

Shell smooth, with sharp collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 5. Cephalis subspherical, with a conical horn twice the length, nearly hyaline, with very small and scarce pores. Thorax nearly spherical, with regular, circular, quincuncial pores. Mouth only half as broad, with nine broad, triangular feet, twice as long as the cephalis, and curved inwards, convergent towards the main axis.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.11 long, 0.12 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

10. Anthocyrtis ovata, n. sp. (Pl. [62], fig. 13).

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 3. Cephalis ovate, with numerous small pores, and an excentric conical horn of the same length. Thorax ovate, with regular, circular, quincuncial pores. Mouth nearly of the same breadth, scarcely constricted, with nine triangular, widely-separated feet, about as long as the cephalis, and convergent towards the main axis.

Dimensions.—Cephalis 0.035 long, 0.03 broad; thorax 0.15 long, 0.1 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Genus 567. Anthocyrtium,[[184]] n. gen.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous terminal feet around the mouth (twelve to fifteen or more). Cephalis free, with an apical horn.

The genus Anthocyrtium has been derived from the two preceding genera by further multiplication of the terminal feet, the number of which is at least twelve to fifteen, often twenty or more. It may be that some species have arisen directly from Patagospyris by loss of the sagittal ring.

Subgenus 1. Anthocyrtarium, Haeckel.

Definition.—Feet of the peristome-corona divergent, their basal distance less than their terminal distance.

1. Anthocyrtium chrysanthemum, n. sp. (Pl. [62], fig. 14).

Shell smooth, with distinct collar stricture. Length of the two joints = 3 : 7, breadth = 4 : 9. Cephalis hemispherical, with small, circular pores, and a large, straight, cylindro-conical horn, about as long as the shell. Thorax campanulate, hemispherical, with six to eight transverse rows of squarish pores, increasing in size downwards. Mouth little constricted, with twelve to fifteen divergent, curved, slender feet, about as long as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Central Pacific, Station 270 to 274, depth 2350 to 2925 fathoms.

2. Anthocyrtium centaurea, Haeckel.

Anthocyrtis mespilus, var. major, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. vi. fig. 5.

Shell smooth, with sharp collar stricture. Length of the two joints = 2 : 6, breadth = 3 : 7. Cephalis hemispherical, with irregular, roundish pores, and a very large pyramidal horn, longer than the shell, with contorted edges. Thorax hemispherical, with six to eight transverse rows of regular, circular pores of equal size. Mouth little constricted, with fifteen to twenty divergent, curved, slender feet, about as long as the shell.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.07 broad.

Habitat.—Fossil in Barbados.

3. Anthocyrtium anthemis, n. sp.

Shell papillate, with obliterated collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis hemispherical, with very small and scarce pores, and a conical horn of the same length. Thorax conical, as long as broad, with conical papillæ, and eight to ten transverse rows of roundish pores, gradually increasing in size downwards. Mouth scarcely constricted, with fifteen to twenty divergent, straight, conical feet, half as long as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.09 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

4. Anthocyrtium collare, Haeckel.

Anthocyrtis collaris, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 8.

Shell rough, conical, with obliterated collar stricture. Length of the two joints = 3 : 5, breadth = 4 : 7. Cephalis conical, with a pyramidal horn of the same length, and with two transverse rows of rather oblong, narrow pores. Thorax truncate, conical, in the lower part thorny, with six to eight transverse rows of regular, circular pores, increasing in size downwards.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.05 long, 0.07 broad.

Habitat.—Fossil in Barbados.

5. Anthocyrtium adonis, n. sp. (Pl. [62] fig. 20).

Shell rough, with sharp collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 12. Cephalis subspherical, with very small circular pores, and a very long, straight cylindrical, horn, twice to three times as long as the shell. Thorax inflated, ovate, or subspherical, with small regular, circular, hexagonally-framed pores. Mouth strongly constricted, half as broad as the thorax, with fifteen to twenty divergent, broad, lamellar, rectangular feet, as long as the thorax, and so densely placed that their margins come in contact with one another.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Central Pacific, Station 263 to 268, depth 2650 to 3000 fathoms.

6. Anthocyrtium anemone, n. sp.

Shell spiny, with sharp collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 4. Cephalis subspherical, with a conical horn of half the length, hyaline, without pores. Thorax spiny, pear-shaped, inflated, with small and numerous, regular, circular pores. Mouth constricted, half as broad as the thorax, with twelve to fifteen divergent, slender, conical, denticulate feet, half as long as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.14 long, 0.12 broad.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms; also fossil in Barbados.

Subgenus 2. Anthocyrtonium, Haeckel.

Definition.—Feet of the peristome-corona parallel, vertical; their basal and apical distances equal.

7. Anthocyrtium campanula, n. sp. (Pl. [62], fig. 17).

Shell smooth, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis spherical, with a conical horn of the same length. Thorax campanulate, thin-walled, with delicate network of regular, hexagonal pores and thin bars. Mouth little constricted, with twenty to twenty-four parallel, vertical, lanceolate feet, about as long as the cephalis.

Dimensions.—Cephalis 0.03 diameter, thorax 0.09 long, 0.1 broad.

Habitat.—South Pacific, Station 302, depth 1450 fathoms.

8. Anthocyrtium reticulatum, Haeckel.

Thyrsocyrtis reticulata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xii. fig. 10.

Shell rough, with sharp collar stricture. Length of the two joints = 1 : 2, breadth = 1 : 3. Cephalis hemispherical, with a prismatic, denticulate horn of the same length, and small, irregular pores. Thorax campanulate, thorny, thin-walled, with delicate network of irregular, polygonal pores. Mouth little constricted, with twelve (or more) small, parallel, vertical, triangular feet, shorter than the cephalis.

Dimensions.—Cephalis 0.015 long, 0.02 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Fossil in Barbados.

9. Anthocyrtium leptostylum, Haeckel.

Anthocyrtis leptostyla, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 1.

Shell thorny, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 4. Cephalis hemispherical, with small, scarce pores and a slender conical horn of the same length. Thorax spiny, with regular, circular, quincuncial pores. Mouth constricted, half as broad, with twelve to eighteen slender, parallel, vertical feet, about as long as the cephalis.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.1 long, 0.08 broad.

Habitat.—Central Pacific, Stations 266 to 270, depth 2550 to 2925 fathoms; also fossil in Barbados.

10. Anthocyrtium hispidum, Haeckel.

Anthocyrtis hispida, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. viii. fig. 2.

Anthocyrtis hispida, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 540, Taf. xxxiii. fig. 30.

Shell thorny, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 5. Cephalis hemispherical, hyaline, with few very small pores, or without any; with a stout conical horn of twice the length. Thorax spiny, with regular, circular, hexagonally-framed pores (half as broad as the bars between them). Mouth wide open, scarcely constricted, with twelve to fifteen parallel, vertical, broad, lamellar, rectangular feet, reaching nearly the length of the thorax.

Dimensions.—Cephalis 0.02 to 0.03 long, 0.03 to 0.05 broad; thorax 0.07 to 0.09 long, 0.1 to 0.12 broad.

Habitat.—Central Pacific, Stations 263 to 265, depth 2650 to 3000 fathoms; also fossil in Barbados.

11. Anthocyrtium turris, n. sp.

Shell thorny, very similar to Calocyclas turris, Ehrenberg (1875, loc. cit., Taf. xviii. fig. 7), but without fenestrated abdomen. Collar stricture deep. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical, hyaline, without pores, with a stout conical horn of twice the length. Thorax nearly spherical, spiny, with regular, circular, quincuncial pores. Mouth little constricted, with fifteen to twenty parallel, vertical, broad, lamellar, rectangular feet, about as long as the thorax.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.1 long, 0.1 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

12. Anthocyrtium doronicum, n. sp. (Pl. [62], fig. 18).

Shell rough, with sharp collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 3. Cephalis hemispherical, with small, circular pores and a stout conical horn of twice the length. Thorax campanulate, subcylindrical, with regular, circular, quincuncial pores, three to four times as broad as the bars. Mouth scarcely constricted, with twenty-four to thirty vertical, nearly parallel, little curved feet, which are about half as long as the shell, broad, lamellar, rectangular, and in close contact with their edges.

Dimensions.—Cephalis 0.025 long, 0.035 broad, thorax 0.12 long, 0.1 broad.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Subgenus 3. Anthocyrturium, Haeckel.

Definition.—Feet of the peristome-corona convergent, their basal distance greater than their apical distance.

13. Anthocyrtium pyrum, n. sp. (Pl. [62], fig. 12).

Shell smooth, with obliterated collar stricture. Length of the two joints = 2 : 7, breadth = 3 : 8. Cephalis hemispherical, with a small, bristle-shaped horn of half the length. Thorax inflated, subglobose, with regular, circular, quincuncial pores and thin bars. Mouth constricted, only half as broad, with fifteen to twenty small, triangular, convergent feet, shorter than the cephalis. (In another specimen the feet were twice as long, stronger and more convergent, than in the one figured.)

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.8 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

14. Anthocyrtium setosum, Haeckel.

Anthocyrtis setosa, Haeckel, 1862, Monogr. d. Radiol., p. 311.

? Lithopera setosa, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B., B. iv. fig. 23.

Shell spiny, with sharp collar stricture. Length of the two joints = 1 : 2, breadth = 1 : 3. Cephalis hemispherical, with a conical horn of the same length and some accessory spines. Thorax campanulate, with subregular, circular pores. Mouth little constricted, with twenty to thirty small, triangular, convergent feet, about as long as the cephalis. (In Ehrenberg's incomplete figure they are mostly broken off.)

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

15. Anthocyrtium ehrenbergii, Haeckel.

Anthocyrtis ehrenbergii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 100, Taf. iii. fig. 21, a, b.

Shell smooth, with obliterated collar stricture. Length of the two joints = 3 : 10, breadth = 2 : 8. Cephalis subcylindrical, with an excentric, stout, pyramidal horn of the same length. Thorax bottle-shaped, with small, regular, circular pores of equal size. Mouth little constricted, with twenty to thirty small, triangular, convergent feet, about half as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.1 long, 0.08 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Grotte), Stöhr.

16. Anthocyrtium zanguebaricum, Haeckel.

Anthocyrtis zanguebarica, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. ix. fig. 12.

Shell smooth, with slight collar stricture. Length of the two joints = 3 : 10, breadth = 2 : 7. Cephalis subspherical, with an excentric conical horn of the same length. Thorax slender, ovate or bottle-shaped, with irregular, roundish pores increasing in size downwards. Mouth little constricted, with twelve to fifteen small, triangular, convergent feet, about half as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.1 long, 0.07 broad.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms, Pullen.

17. Anthocyrtium ficus, Haeckel.

Anthocyrtis ficus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 3.

Shell rough, with obliterated collar stricture. Length of the two joints = 2 : 12, breadth = 3 : 10. Cephalis conical, with a large, cylindrical horn, pyramidal at the base, about as long as the thorax. Thorax subovate, truncate, papillate, with small, regular, circular, quincuncial pores of the same breadth as the bars. Mouth constricted, two-thirds as broad as the thorax, with fifteen to twenty strongly convergent, lamellar, rectangular or sword-shaped feet, nearly as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.12 long, 0.1 broad.

Habitat.—Fossil in Barbados.

18. Anthocyrtium flosculus, n. sp. (Pl. [62], fig. 19).

Anthocyrtis flosculus, Haeckel, 1881, Prodromus et Atlas, pl. lxii. fig. 19.

Shell ribbed, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 4. Cephalis hemispherical, with small, circular pores and a large cylindrical horn, twice as long as the thorax and half as broad at the base as the cephalis. Thorax subovate, truncate, with twenty-four to thirty longitudinal ribs and alternating rows of circular pores. Mouth constricted, two-thirds as broad as the thorax, with twenty-four to thirty slender, convergent feet, which are as long as the entire shell, with their edges in close contact and their distal ends pointed.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.12 long, 0.12 broad.

Habitat.—Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.

Genus 568. Anthocyrtidium,[[185]] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethophormida, (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous (twelve to fifteen or more) subterminal feet, which are separated from the constricted mouth by a ring of lattice-work. Cephalis free, with an apical horn.

The genus Anthocyrtidium has been derived from the preceding Anthocyrtium by further growth and constriction of the peristome, which becomes separated from the subterminal corona of feet by a more or less broad ring of lattice-work.

1. Anthocyrtidium cineraria, n. sp. (Pl. [62], fig. 16).

Shell campanulate, smooth, with obliterated collar stricture. Length of the two joints = 5 : 11, breadth = 3 : 13. Cephalis subcylindrical-ovate, with a conical straight horn of half the length. Thorax hemispherical, inflated, nearly twice as broad as the constricted mouth. Pores subregular, circular, double-contoured. Above the mouth, separated from it by two rows of pores, a corona of twelve to fifteen short conical feet, which are directed downwards, slightly curved, and as long as the cephalic horn.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax 0.11 long, 0.13 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Anthocyrtidium ligularia, n. sp. (Pl. [62], fig. 15).

Shell campanulate, rough, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 6. Cephalis hemispherical, with a slender, conical, slightly curved horn, about as long as the shell. Thorax hemispherical, three times as broad as the cephalis, nearly twice as broad as the constricted mouth, which is prolonged into a prominent smooth ring. Above the mouth, separated from it by one row of pores, a corona of twelve to fifteen slender linear feet, which are slightly curved, divergent, and emarginate at the truncated distal end.

Dimensions.—Cephalis 0.015 long, 0.03 broad; thorax 0.06 long, 0.09 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Anthocyrtidium matricaria, n. sp.

Shell campanulate, rough, very similar to the preceding species, but differing in the straight, large, pyramidal horn of the cephalis (as long as the shell), and in the longer feet, which are twelve to fifteen in number, little curved at the distal end, pointed, and about as long as the shell. Length of the two joints = 2 : 6, breadth = 3 : 8. Differs from the similar Anthocyrtium centaurea, Ehrenberg (1875, loc. cit., Taf. vi. fig. 5), mainly in the prominent ring of the peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Genus 569. Carpocanium,[[186]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous terminal feet around the mouth (six to twelve or more). Cephalis hidden in the thorax, without apical horn.

The genus Carpocanium, very common, and rich in numerous living and fossil species, was formerly placed by me among the true Monocyrtida, since an external constriction is not visible (Monogr., 1862, p. 290). Afterwards (in 1879) Richard Hertwig demonstrated that the cavity of the ovate shell, externally simple, is divided by an internal transverse septum into two joints, the upper of which is the flat rudimentary cephalis (Organism. d. Radiol., p. 79; compare also Bütschli, 1882, loc. cit., p. 535). Indeed this septum, with four central crossed cortinar beams, is a true collar septum, and Carpocanium has been derived from Anthocyrtis or Desmospyris by reduction of the cephalis, which is very flat and perfectly hidden in the uppermost part of the thorax. The apical horn is lost. If the internal septum were to become lost, the genus would pass over into Carpocanistrum.

Subgenus 1. Carpocanarium, Haeckel.

Definition.—Peristome-corona composed of six feet (three primary perradial alternating with three secondary interradial).

1. Carpocanium calycodes, Stöhr.

Carpocanium calycodes, Stöhr, 1880, Palæontogr., vol. xxvi. p. 96, Taf. iii. fig. 8.

Shell urceolate, smooth, nearly twice as long as broad, with hemispherical vaulted cephalis. Length of the two joints = 3 : 16, breadth = 5 : 10. Pores regular, circular, as broad as the bars, quincuncially disposed in about five longitudinal series at each side. Mouth constricted, half as broad as the thorax. Peristome with six vertical, equilateral, triangular feet.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax 0.08 long, 0.05 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Grotte, Caltanisetta).

2. Carpocanium setosum, Haeckel.

Halicalyptra setosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160, Taf. ii. fig. 12.

Shell ovate, truncate at the mouth, thorny, exactly as long as broad. Length of the two joints = 1 : 8, breadth = 3 : 9. Cephalis hidden, with very small pores. Thorax inflated, with regular, circular pores, twice as broad as the bars, in about ten longitudinal series at each side. Mouth constricted, half as broad as the thorax. Peristome with six vertical, parallel, broad, lamellar, rectangular feet, separated by equal internals, half as long as the shell.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Fossil in Barbados.

3. Carpocanium laeve, Ehrenberg.

Carpocanium laeve, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287.

Shell subspherical, smooth, equal in length and breadth, with little vaulted, cap-shaped cephalis. Length of the two joints = 1 : 6, breadth = 4 : 7. Pores regular, circular, twice as broad as the bars, in nine longitudinal rows. Mouth constricted, only one-third as broad as the thorax. Peristome with six strong conical feet, which are slightly curved and convergent.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.06 long, 0.07 broad.

Habitat.—Mediterranean (Greece); Tropical Atlantic, Station 348, depth 2450 fathoms.

4. Carpocanium lanceolatum, n. sp.

Shell subspherical, thorny, with perfectly hidden cephalis. Length of the two joints = 1 : 3, breadth = 1 : 3. Pores regular, circular, hexagonally framed, half as broad as the bars, in about sixteen longitudinal rows at each side. Mouth constricted, half as broad as the thorax. Peristome with six large lanceolate, vertical, lamellar feet, half as long as the shell.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.09 long, 0.09 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Subgenus 2. Carpocanidium, Haeckel.

Definition.—Peristome-corona composed of nine feet (three primary perradial and six secondary interradial).

5. Carpocanium diadema, Haeckel.

Carpocanium diadema, Haeckel, 1862, Monogr. d. Radiol., p. 290, Taf. v. fig. 1.

Carpocanium diadema, R. Hertwig, 1879, Organism. d. Radiol., p. 79, Taf. viii. figs. 7, 7a, 8, 8a, 8b.

Shell ovate, with little vaulted cephalis. Length of the two joints = 1 : 8, breadth = 3 : 6. Pores regular, circular, in about twelve longitudinal rows, twice as broad as the bars. Mouth constricted, half as broad as the thorax. Peristome with nine vertical, equilateral, triangular feet.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; many stations, surface.

6. Carpocanium cylindricum, n. sp.

Shell cylindrical, with hemispherical, flatly vaulted cephalis. Length of the two joints = 1 : 4, breadth = 3 : 3. Pores regular, circular, double-contoured, as broad as the bars, in about fifteen longitudinal series. Mouth constricted, two-thirds as broad as the thorax. Peristome with nine vertical, slender, triangular, pointed feet.

Dimensions.—Cephalis 0.02 long, 0.06 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

7. Carpocanium enneaphyllum, n. sp.

Shell slenderly ovate, at the mouth truncate, thorny, with hemispherical, vaulted cephalis. Length of the two joints = 1 : 6, breadth = 2 : 4. Pores regular, circular, hexagonally framed, as broad as the bars, in about thirteen longitudinal rows. Mouth constricted, about two-thirds as broad as the thorax. Peristome with nine broad, lamellar, vertical, nearly square feet, half as long as the shell, with small intervals.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.09 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

8. Carpocanium solitarium, Ehrenberg.

Carpocanium solarium, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 28.

Lithocampe solitaria, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 65.

Shell slenderly ovate, twice as long as broad, with hidden spherical cephalis, completely enclosed in the summit of the thorax. Length of the two joints = 1 : 6, breadth = 1 : 4. Pores small, regular, circular, as broad as the bars, in about eleven longitudinal rows. Mouth gradually constricted, half as broad as the thorax. Peristome with nine ovate blunt feet, which are as long as the cephalis, little curved and convergent.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.12 long, 0.07 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Caltanisetta).

9. Carpocanium gemmula, n. sp.

Shell subspherical, smooth, equal in length and breadth, with hemispherical vaulted cephalis. Length of the two joints = 2 : 7, breadth = 4 : 9. Pores small, regular, circular, twice as broad as the bars, in about twenty longitudinal rows. Mouth strongly constricted, only one-fourth as broad as the thorax. Peristome with nine conical feet, which are twice as long as the cephalis, curved, and so convergent that their distal ends come nearly in contact.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

10. Carpocanium microdon, Ehrenberg.

Carpocanium microdon, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 30.

Shell broad, ovate, rough, with perfectly hidden cephalis. Length of the two joints = 2 : 9, breadth = 4 : 7. Pores very small and scarce, smaller than the bars between them, irregularly scattered. Mouth constricted, one-third as broad as the thorax. Peristome with nine short, triangular, pointed, convergent feet.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Mediterranean (Crete), Atlantic (Canary Islands), Station 354, surface.

Subgenus 3. Carpocanobium, Haeckel.

Definition.—Peristome-corona composed of twelve or more feet.

11. Carpocanium trepanium, n. sp. (Pl. [52], fig. 18).

Shell subcylindrical, with flatly vaulted cephalis. Length of the two joints = 1 : 6, breadth = 3 : 4. Pores regular, hexagonal, four to six times as broad as the bars. Mouth little constricted, two-thirds as broad as the thorax. Peristome with eighteen to twenty-four large, slender, triangular, vertical feet.

Dimensions.—Cephalis 0.02 long, 0.06 broad; thorax 0.12 long, 0.08 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

12. Carpocanium hexagonale, n. sp. (Pl. [52], fig. 15).

Shell broadly ovate or subconical, with vaulted, cap-shaped cephalis. Length of the two joints = 2 : 7, breadth = 6 : 9. Thorax subglobular, truncate. Pores subregular, hexagonal, three to four times as broad as the bars. Mouth constricted, two-thirds as broad as the thorax. Peristome with twenty to twenty-five small, triangular, vertical feet.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Tropical Atlantic, Station 347, surface.

13. Carpocanium petalospyris, n. sp. (Pl. [52], fig. 19).

Shell subspherical, smooth, with perfectly hidden cephalis. Length of the two joints = 1 : 6, breadth = 3 : 6. Pores regular, circular, hexagonally framed, twice as broad as the bars, in about sixteen longitudinal rows. Mouth slightly constricted, little narrower than the thorax. Peristome with twenty to twenty-four vertical, broad, lamellar feet, which are nearly as long as the shell, at the distal end truncate, and almost in contact at their edges.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.11 long, 0.12 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

14. Carpocanium polypterum, Haeckel.

Cryptoprora polyptera, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ix. fig. 17.

Carpocanium macropterum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 302.

Shell campanulate-conical, smooth, with perfectly hidden cephalis. Length of the two joints = 1 : 6, breadth = 4 : 6. Pores regular, circular, twice as broad as the bars, in about sixteen longitudinal rows. Mouth wide open, not constricted. Peristome with twenty to thirty vertical, slender, conical feet, about as long as the shell.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.06 long, 0.06 broad.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms (Pullen).

15. Carpocanium palmipes, n. sp.

Shell ovate, very thick-walled, smooth. Lower half of the subspherical cephalis hidden in the summit of the thorax, upper half free, with few small pores. Length of the two joints = 3 : 10, breadth = 3 : 10. Thorax foveolate, with oblong dimples, each of which encloses a small, circular, double-contoured pore, half as broad as the bars. Mouth little constricted, nearly as broad as the thorax. Peristome prolonged into a solid, cylindrical tube, nearly as long and as broad as the shell; the upper half of the tube is solid, the lower divided into from twelve to fifteen vertical, lamellar, pointed feet.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.1 long, 0.1 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

16. Carpocanium peristomium, n. sp. (Pl. [52], figs. 16, 17).

Shell ovate, smooth, with perfectly hidden, flat cephalis (fig. 17). Length of the two joints = 2 : 10, breadth = 5 : 9. Pores small and very numerous, regular, circular, as broad as the bars, in about twenty longitudinal rows. Mouth little constricted. Peristome broad; in the upper half a hyaline, circular ring, in the lower half divided into from eighteen to twenty-four triangular, curved, little convergent feet.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.1 long, 0.09 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; many stations, at various depths.

17. Carpocanium coronatum, Ehrenberg.

Carpocanium coronatum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. v. fig. 7.

Shell ovate, smooth, with perfectly hidden, subspherical cephalis. Length of the two joints = 2 : 9, breadth = 2 : 8. Pores small and very numerous, twice as broad as the bars, regular, circular, in about twenty longitudinal rows. Mouth little constricted, two-thirds as broad as the thorax. Peristome with twenty-five to thirty short, bristle-shaped feet, which are slightly curved, convergent, and in the upper half connected by a solid ring.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Fossil in Barbados.

18. Carpocanium dactylus, n. sp.

Shell slenderly ovate, twice as long as broad, with flat, perfectly hidden cephalis. Length of the two joints = 1 : 12, breadth = 4 : 8. Pores subregular, circular, as broad as the bars, in about twelve longitudinal rows, separated by prominent longitudinal ribs. Mouth constricted, two-thirds as broad as the thorax. Peristome with twelve large, lanceolate, lamellar, convergent feet.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

19. Carpocanium irregulare, n. sp. (Pl. [52], fig. 14).

Shell irregular, roundish, subovate, with flat and oblique, perfectly hidden cephalis. Length of the two joints = 1 : 10, breadth = 3 : 9. Pores irregularly scattered, roundish, about as broad as the bars. Mouth wide open, not at all or little constricted. Peristome with twenty to thirty long, lamellar, pointed feet, which are irregularly curved and convergent.

Dimensions.—Cephalis 0.01 to 0.02 long, 0.03 to 0.04 broad; thorax 0.09 to 0.11 long, 0.08 to 0.09 broad.

Habitat.—Central Pacific, Station 263 to 274, surface, and at various depths.

20. Carpocanium verecundum, n. sp. (Pl. [52], figs. 12, 13).

Shell ovate, smooth, with flat, perfectly hidden cephalis (fig. 12). Length of the two joints = 1 : 9, breadth = 4 : 9. Pores subregular, circular, twice as broad as the bars, in about eighteen, partly interrupted, longitudinal rows, separated by prominent crests. Mouth little constricted. Peristome with twenty to twenty-four broad, lamellar, pointed feet, which are about as long as the shell, little curved, and convergent.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.09 long, 0.09 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

21. Carpocanium virgineum, n. sp. (Pl. [52], fig. 20).

Shell ovate, smooth, with flat perfectly hidden cephalis. Length of the two joints = 1 : 8, breadth = 3 : 9. Pores regular, circular, hexagonally framed, as broad as the bars, in about sixteen longitudinal rows on each side. Mouth little constricted. Peristome with eighteen to twenty-four very large, lamellar, pointed feet, which are longer than the shell, and so curved and convergent that their distal points come nearly in contact.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Subfamily 2. Sethophænida, Haeckel, 1881, Prodromus, p. 433.

Definition.—Anthocyrtida with the basal mouth of the shell fenestrated (vel Dicyrtida multiradiata clausa).

Genus 570. Sethophæna,[[187]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethophænida (vel Dicyrtida multiradiata clausa) with lateral apophyses. Cephalis with a horn.

The genus Sethophæna and the following Clistophæna form together the small subfamily of Sethophænida, comprising those Dicyrtida in which the thorax bears numerous radial appendages (four to six or more), and the mouth is closed by a lattice-plate. In Sethophæna the apophyses are lateral wings, as in Micromelissa, from which it may be derived by development of secondary wings, interpolated between the three primary wings.

1. Sethophæna tetraptera, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 9. Cephalis subspherical, without horn. Thorax ovate, with rounded hemispherical base, and subregular, hexagonal pores. From its upper half (below the collar stricture) arise four divergent, conical, straight wings, of half the length, opposite in pairs in two meridional planes, perpendicular to one another (compare Tetralacorys, Pl. [65], figs. 4, 5).

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.09 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

2. Sethophæna hexaptera, n. sp. (Pl. [97], fig. 13).

Shell rough, pear-shaped, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 4. Cephalis hemispherical, with a conical horn of the same length. Thorax inflate, inversely ovate, nearly pear-shaped, with subregular, circular pores. From its upper half arise, by a broad base, six divergent, strong, conical wings, which are horn-like, curved downwards, and half as long as the thorax.

Dimensions.—Cephalis 0.025 long, 0.04 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

3. Sethophæna enneaptera, n. sp.

Shell rough, with sharp collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 3. Cephalis subspherical, with a stout conical horn of twice the length. Thorax inversely ovate, with pointed, conical, basal part, and irregular, roundish pores. From its middle part arise, by a broad triangular base, nine compressed, divergent wings, which are a little curved, slender, and about as long as the thorax.

Dimensions.—Cephalis 0.025 long, 0.03 broad; thorax 0.17 long, 0.1 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

4. Sethophæna polyptera, n. sp.

Shell thorny, with slight collar stricture. Length of the two joints = 1 : 10, breadth = 3 : 8. Cephalis flat, cap-shaped, without horn. Thorax pear-shaped, with hemispherical base and regular, circular pores. From its lower half (beyond the equator) arises a corona of numerous short conical wings (eighteen to twenty-four), which are a little curved, and divergent downwards, scarcely one-third as long as the thorax.

Dimensions.—Cephalis 0.015 long, 0.04 broad; thorax 0.15 long, 0.12 broad.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 571. Clistophæna,[[188]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethophænida (vel Dicyrtida multiradiata clausa) with terminal apophyses. Cephalis with a horn.

The genus Clistophæna agrees with the preceding Sethophæna in the mouth of the thorax being closed by a lattice-plate. But the appendages of the thorax are terminal feet, not lateral wings; their number is commonly six or nine, rarely more. Clistophæna may be derived either from Tetrahedrina by interpolation of secondary feet between the three primary, or from Sethamphora by development of a basal lattice-plate closing the mouth.

1. Clistophæna rüstiana, n. sp. (Pl. [57], fig. 6).

Shell rough, with distinct collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 11. Cephalis hemispherical, with small, circular pores and a stout oblique horn three times the length, which is three-sided prismatic, and at the top denticulate. Thorax subconical, inflate, with regular, circular, quincuncial pores, increasing in size towards the base. Margin of the flat base, with six divergent, stout feet of the same prismatic form as the cephalic horn, with denticulate distal ends, about as long as the thorax. This elegant species is dedicated to Dr. Rüst of Freiburg, the discoverer of numerous fossil Radiolaria in the Liassic and Jurassic formations.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.11 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Clistophæna hexolena, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subspherical, small, with a large, vertical, cylindrical horn, about as long as the shell, and small, circular pores. Thorax nearly three-sided pyramidal or tetrahedral, with three rounded edges and sub-regular, circular pores. Margin of the flat base with six conical, divergent, straight feet, somewhat shorter than the thorax. (Three on the corners, one on the middle of each side of the triangular base.)

Dimensions.—Cephalis 0.03 diameter, thorax 0.12 long, 0.14 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

3. Clistophæna pyramidalis, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 2 : 8, breadth = 3 : 10. Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax six-sided pyramidal, with regular, circular pores of equal size, and six prominent, straight edges, which are prolonged into six divergent, pyramidal feet of half the length.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

4. Clistophæna armata, n. sp. (Pl. [57], fig. 7).

Shell spiny, with deep collar stricture. Length of the two joints = 4 : 18, breadth = 5 : 15. Cephalis subspherical, with small, circular, hexagonally-framed pores, and a stout, three-sided prismatic, cuspidate horn of the same length. Thorax pear-shaped, with regular, circular pores and three pairs of stout pyramidal wings, placed in the three primary meridional planes of the collar beams; three of them lie in the upper, and three in the lower third of the thorax. Margin of the flat base with nine cylindrical, somewhat club-shaped, divergent feet.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.18 long, 0.15 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

5. Clistophæna enneolena, n. sp.

Shell spiny, with sharp collar stricture. Length of the two joints = 4 : 20, breadth 5 : 16. Cephalis hemispherical, hyaline, with a stout conical horn of the same length and some small accessory horns. Thorax ovate, spiny, with subregular, circular pores. Margin of the vaulted base with nine divergent, conical feet, half as long as the thorax.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.2 long, 0.16 broad.

Habitat.—South Pacific, Station 296, depth 1825 fathoms.

6. Clistophæna polyolena, n. sp.

Shell smooth, conical, with obliterated collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 5. Cephalis hemispherical, with small, circular pores and two divergent conical horns (a major occipital and a smaller frontal horn). Thorax obtusely conical, with regular, hexagonal pores at the mantle, and circular pores in the basal plate, the margin of which bears eighteen vertical, parallel, conical feet, as long as the cephalis.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

Family LXIV.—Sethocyrtida, n. fam.

Sethocorida et Sethocapsida, Haeckel, 1881, Prodromus, pp. 439, 433.

Definition.—Dicyrtida eradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, without radial apophyses).

The family Sethocyrtida, composed of the Sethocorida and Sethocapsida of my Prodromus, comprises those Cyrtoidea in which the shell is two-jointed and bears no radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethocorida is a simple wide opening, and in the Sethocapsida is closed by a lattice-plate. The former are here divided into eight, the latter into three genera.

Numerous living and fossil forms of Sethocyrtida were previously described by Ehrenberg, partly in his genera Dictyocephalus and Lophophæna, partly (intermingled with three-jointed and many-jointed forms) in the genera Eucyrtidium and Lithocampe. A larger number of new forms has been found in the Radiolarian ooze collected by the Challenger, and others fossil in Barbados. Many of these Sethocyrtida are common and widely distributed. When a new third joint is formed on their basal mouth, they pass over into Theocyrtida.

The cephalis is usually subspherical or hemispherical, and much smaller than the thorax, the form of which exhibits all possible intermediate stages between flat, discoidal, conical, cylindrical, and ovate forms. The wide open mouth becomes more and more constricted, and finally closed in the Sethocapsida. The majority of the Sethocyrtida may have been derived either from the Tripocyrtida, or from the Anthocyrtida by reduction and loss of the radial apophyses.

Synopsis of the Genera of Sethocyrtida.

I. Subfamily Sethocorida.

Terminal mouth of the thorax a simple wide opening.

Thorax conical or campanulate, gradually dilated.Shell simple, without mantle,572. Sethoconus.
Shell double, with an arachnoid mantle,573. Periarachnium.
Thorax discoidal, flatly expanded.Cephalis very large, without horn,574. Sethocephalus.
Thorax cylindrical or ovate, with truncate, constricted or tubular mouth.Cephalis with a single horn.Mouth simple,575. Sethocyrtis.
Mouth tubular,576. Sethocorys.
Cephalis with two horns or a bunch of horns,577. Lophophæna.
Cephalis without horn,578. Dictyocephalus.

II. Subfamily Sethocapsida.

Terminal mouth closed by a lattice-plate.

Cephalis free, not hidden in the thorax.One horn,579. Sethocapsa.
No horn,580. Dicolocapsa.
Cephalis hidden in the upper part of the thorax.No horn,581. Cryptocapsa.

I. Subfamily Sethocorida.

Terminal mouth of the thorax a simple wide opening.

Thorax conical or campanulate, gradually dilated.
Shell simple, without mantle,
572. Sethoconus.
Shell double, with an arachnoid mantle,
573. Periarachnium.
Thorax discoidal, flatly expanded.
Cephalis very large, without horn,
574. Sethocephalus.
Thorax cylindrical or ovate, with truncate, constricted or tubular mouth.
Cephalis with a single horn.
Mouth simple,
575. Sethocyrtis.
Mouth tubular,
576. Sethocorys.
Cephalis with two horns or a bunch of horns,
577. Lophophæna.
Cephalis without horn,
578. Dictyocephalus.

II. Subfamily Sethocapsida.

Terminal mouth closed by a lattice-plate.

Cephalis free, not hidden in the thorax.
One horn,
579. Sethocapsa.
No horn,
580. Dicolocapsa.
Cephalis hidden in the upper part of the thorax.
No horn,
581. Cryptocapsa.

Subfamily 1. Sethocorida, Haeckel, Prodromus, p. 430.

Definition.—Sethocyrtida with the basal mouth of the shell open (vel Dicyrtida eradiata aperta).

Genus 572. Sethoconus,[[189]] Haeckel, 1881, Prodromus, p. 430.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with conical or campanulate, gradually dilated thorax and wide open mouth. Cephalis with one or more horns.

The genus Sethoconus is the oldest and simplest form of the Sethocorida, or of those Dicyrtida in which the simple thorax bears no apophyses and has the mouth open and not closed by a basal lattice-plate. Probably all those eradiate Sethocorida have been derived either from triradiate Sethopilida (Lychnocanium), or from multiradiate Sethophormida (Sethophormis, Anthocyrtis ?) by loss of the radial ribs and feet. In Sethoconus the thorax is more or less conical, sometimes more campanulate, commonly smooth, in some species covered with spines. The cephalis is usually small, with rudimentary collar septum, at other times large, with distinct cortinar septum. Correspondingly, the genus may be divided into different groups, which here are enumerated as subgenera.

Subgenus 1. Conarachnium, Haeckel, 1881, Prodromus, p. 430. (= Ceratocyrtis, Bütschli), 1882, loc. cit., p. 536.

Definition.—Cephalis relatively large, with distinct collar septum and numerous pores. Thorax smooth.

1. Sethoconus trochus, Haeckel.

Eucyrtidium trochus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii, fig. 17.

Conarachnium trochus, Haeckel, 1881, Prodromus, p. 430.

Cephalis ovate, relatively large, with a pyramidal horn of the same length, and three pairs of large opposite pores, on each side of a vertical septum. Thorax wide, conical, about as long as broad, with nearly straight outlines; its pores regular, circular, hexagonally framed, of the same size as the cephalic pores.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.06 long, 0.06 broad.

Habitat.—Tropical Pacific, Stations 200 to 281, surface.

2. Sethoconus cucullaris, Haeckel.

Cornutella cucullaris, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 7.

Ceratocyrtis cucullaris, Bütschli, 1882, Zeitschr. f. wiss Zool., Bd. xxvi. p. 536, Taf. xxxiii. fig. 36, a., b.

Cephalis subspherical, thorny, relatively large, with a conical horn of the same length, and small circular pores. Thorax wide, conical, enveloping the lower hidden half of the cephalis, about as long as broad, with slightly convex outlines; its pores subregular, circular, half as broad as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.15 long, 0.14 broad.

Habitat.—Fossil in Barbados.

3. Sethoconus pileus, n. sp.

Cephalis subspherical, free, with distinct collar stricture, a conical oblique horn of the same length, and small, irregular, roundish pores. Thorax flatly conical, about half as long as broad, with straight outlines; its pores subregular, hexagonal, half as broad as the cephalis, with very thin bars.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.08 long, 0.16 broad.

Habitat.—Central Pacific, Stations 262 to 274, surface.

4. Sethoconus ampliatus, Haeckel.

Cornutella ampliata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 5.

Ceratocyrtis ampliata, Bütschli, 1882, Zeitschr. f. wiss. Zool., Bd. xxxvi. p. 536.

Cephalis, hemispherical, thorny, with a conical horn of twice the length; it is separated from the thorax by a complete internal collar septum, but without external collar stricture. Thorax flatly conical, about half as long as broad, with straight outlines; its pores subregular, hexagonal, about as large as the cephalis, with thin bars.

Dimensions.—Cephalis 0.015 long, 0.03 broad; thorax 0.08 long, 0.18 broad.

Habitat.—Fossil in Barbados.

5. Sethoconus mitra, Haeckel.

Cornutella mitra, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 8.

Ceratocyrtis mitra, Bütschli, 1882, Zeitschr. f. wiss. Zool., Bd. xxxvi. p. 536.

Cephalis ovate, with slight collar stricture (not distinct enough in Ehrenberg's figure), with few large pores, and a conical stout horn of the same length. Thorax campanulate, conical, twice as long as broad, with slightly convex outlines; its pores subregular, roundish, increasing in size towards the mouth, the largest as broad as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.12 long, 0.07 broad.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms; fossil in Barbados.

6. Sethoconus rayianus, n. sp. (Pl. [58], fig. 6).

Conarachnium rayianum, Haeckel, 1881, Prodromus, p. 430.

Cephalis ovate, with obliterated collar stricture (but distinct internal septum), with small, irregular pores, and two to four divergent horns, which are longer than the cephalis, and two or three of which are forked. Thorax tent-shaped, conical, two-thirds as long as broad, with slightly concave outlines, and subregular, hexagonal pores, gradually increasing towards the mouth, the largest half as broad as the cephalis. This elegant species is dedicated to Dr. Ray, the discoverer of many rare Radiolarians in the Challenger collection.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.08 long, 0.12 broad.

Habitat.—Central Pacific, Stations 266 to 272, surface.

7. Sethoconus cervus, Haeckel.

? Eucyrtidium cervus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 291, Taf. ix. fig. 21.

Conarachnium cervus, Haeckel, 1881, Prodromus, p. 430.

Cephalis subspherical, with slight collar stricture, small circular pores, and two to four divergent horns, one or two of which are forked. Thorax wide, conical, about as long as broad, with straight outlines and irregular, polygonal pores, gradually increasing towards the mouth; the largest as broad as the cephalis.

Dimensions.—Cephalis 0.015 long, 0.02 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Indian Ocean; Maldive Islands, surface (Haeckel); Zanzibar, depth 2200 fathoms (Pullen).

8. Sethoconus lophophæna, n. sp.

Conarachnium lophophæna, Haeckel, 1881, Prodromus, p. 430.

Cephalis subspherical, with distinct collar stricture, small circular pores, and numerous (twelve to sixteen) radial, bristle-shaped horns of different lengths. Thorax wide, conical, somewhat longer than broad, with slightly convex outlines, and subregular, hexagonal pores, increasing gradually in size towards the mouth; the largest twice as broad as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.2 long, 0.16 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

9. Sethoconus larvatus, Haeckel.

Lophophæna larvata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 10.

Dictyocephalus larvatus, Bütschli, 1882, Zeitschr. f. wiss. Zool., Bd. xxxvi. p. 535.

Cephalis subspherical, large, with sharp collar stricture, and numerous (five to ten or more) radial, conical (partly forked) horns of different lengths. Thorax wide, conical, somewhat broader than long, with straight outlines. Pores of both joints very irregular, roundish, of very different sizes and form.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Fossil in Barbados.

10. Sethoconus nassa, Haeckel.

Eucyrtidium nassa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 72, Taf. ix. fig. 9.

Cephalis slenderly ovate, with sharp collar stricture, few scattered pores, and a very stout, pyramidal horn of the same length, which is surrounded at the base by three short, divergent, ascending spines (perhaps the remnants of the three cortinar rods of Eucecryphalus, &c. ?). Thorax slender, conical, with straight outlines, and small, dense, regular, circular pores of equal size.

Dimensions.—Cephalis 0.04 long, 0.02 broad; thorax 0.12 long, 0.08 broad.

Habitat.—Fossil in Barbados.

11. Sethoconus tabulatus, Haeckel.

Cycladophora tabulata, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. iv. fig. 18.

Cephalis subspherical, with slight collar stricture, and numerous small, irregular pores, without horn, or with a small conical horn. Thorax slenderly conical, with straight outlines, and large, regular, hexagonal pores. Mouth truncate. (In the specimen I examined the thorax was longer and more conically dilated; the cephalis had a distinct small horn.)

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.06 broad.

Habitat.—North Atlantic, Antilles, depth 1600 fathoms (Ehrenberg); Station 347, depth 2250 fathoms.

Subgenus 2. Cornutellium (vel Ceratarachnium), Haeckel, 1881, Prodromus, p. 430.

Definition.—Cephalis very small, rudimentary, hyaline, without distinct collar septum, and without pores (or with scarce, rudimentary pores). Thorax smooth.

12. Sethoconus hexagonalis, Haeckel.

Cornutella trochus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ix. fig. 14.

Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the length. Thorax slenderly conical, or bottle-shaped, twice to three times as long as broad; in the lower half nearly cylindrical, with very thin, thread-like bars, and regular, hexagonal pores, increasing in size towards the mouth.

Dimensions.—Cephalis 0.005 diameter, thorax 0.12 long, 0.05 broad.

Habitat.—Indian Ocean, Zanzibar, depth 2200 fathoms (Pullen).

13. Sethoconus verrucosus, Haeckel.

Cornutella verrucosa, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ix. fig. 16.

Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the length. Thorax slenderly conical, or bottle-shaped, with little convex outlines; three to four times as long as broad, papillate, with regular, circular pores, which are included by rhombic frames, and increase in size towards the mouth.

Dimensions.—Cephalis 0.004 diameter, thorax 0.12 long, 0.035 broad.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms (Pullen).

14. Sethoconus orthoceras, n. sp. (Pl. [54], fig. 11).

Cornutella orthoceras, Haeckel, 1879, Atlas, loc. cit.

Cephalis very small, conical, hyaline, without pores, with a double internal stricture, and a very short, rudimentary horn. Thorax slenderly conical, with undulate outlines, three to four times as long as broad, with subregular, roundish pores, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.02 long, 0.01 broad; thorax 0.16 long, 0.04 to 0.08 broad.

Habitat.—South Atlantic, Station 325, surface.

15. Sethoconus profundus, Haeckel.

Cornutella profunda, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B, Nr. B. iv. fig. 21.

Cornutella profunda, Bailey, 1856, Amer. Jour., vol. xxii. pl. i. fig. 23.

Cornutella profunda, Haeckel, 1862 Monogr. d. Radiol., p. 284.

Cephalis very small, spherical, hyaline without pores and internal stricture, with a very short, rudimentary horn. Thorax slenderly conical with straight outlines, three to four times as long as broad, with subregular, circular pores, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.004 to 0.008 diameter, thorax 0.08 to 0.12 long, 0.03 to 0.04 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; at various depths.

16. Sethoconus trichostylus, Haeckel.

Cornutella trichostyla, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vi. fig. 2.

Cephalis very small, conical, hyaline, without pores, with a very long, bristle-shaped, spirally twisted horn, longer than the whole shell. Thorax slenderly conical, with straight outlines, and very small, regular, circular pores of nearly equal size, which are separated by broader bars and spirally ascending oblique crests (according to the figure).

Dimensions.—Cephalis 0.004 long, 0.002 broad; thorax 0.06 long, 0.04 broad.

Habitat.—North Pacific (California), depth 2600 fathoms.

17. Sethoconus longisetus, Haeckel.

Cornutella longiseta, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ix. fig. 15.

Cephalis very small, spherical, hyaline, without pores, with a very long, bristle-shaped horn, nearly as long as the shell. Thorax slenderly conical, rough, with straight outlines, and irregular, roundish pores, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.01 diameter, thorax 0.09 long, 0.03 broad.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms (Pullen).

18. Sethoconus gracilis, Haeckel.

Eucyrtidium gracile, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xi. fig. 15.

Cephalis small, subspherical, with few scarce pores, and a stout, pyramidal horn, of the same length. Thorax slenderly conical, three to four times as long as broad, with straight outlines, and very small and numerous circular pores of equal size.

Dimensions.—Cephalis 0.015 diameter, thorax 0.12 long, 0.04 broad.

Habitat.—Fossil in Barbados.

19. Sethoconus bimarginatus, n. sp. (Pl. [54], fig. 12).

Cornutella bimarginata, Haeckel, 1879, Atlas, loc. cit.

Cephalis very small, subspherical, hyaline, without pores, with a rudimentary, conical horn of the same length. Thorax slenderly conical, three times as long as broad, with undulated, little convex outlines, and irregular, roundish, double-contoured pores, arranged in nine longitudinal series, markedly increasing in size towards the mouth.

Dimensions.—Cephalis 0.01 diameter, thorax 0.16 long, 0.05 broad.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

20. Sethoconus clathratus, Haeckel.

Cornutella clathrata, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 39a, b, c.

Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the length. Thorax slenderly conical, three to four times as long as broad, smooth, with curved axis and small, regular, circular pores, nearly equal in size. This common species differs from all others of the genus by the curvation of the axis of the shell, which is more or less crescentic, or curved like a cowherd's horn; it may, therefore, represent a peculiar genus, Sethodrepanum.

Dimensions.—Cephalis 0.003 to 0.006 diameter, thorax 0.08 to 0.16 long, 0.03 to 0.05 broad.

Habitat.—Cosmopolitan; Atlantic, Pacific, many stations; fossil in Barbados and Sicily.

Subgenus 3. Phlebarachnium, Haeckel (et Cladarachnium, Haeckel), 1881,

Definition.—Cephalis small, with very small pores, and internal collar septum. Thorax spiny or thorny.

21. Sethoconus facetus, n. sp. (Pl. [55], fig. 1).

Phlebarachnium facetum, Haeckel, 1881, Prodromus, p. 430.

Cephalis small, hemispherical, with distinct collar septum, the same network as the thorax, and numerous bristle-shaped horns of the same length. Thorax wide, conical, about as long as broad, with slightly convex outlines; its network extremity delicate, with very small and numerous, regular, hexagonal pores, disposed in numerous divergent, longitudinal series, which are convoluted somewhat spirally around the shell axis. Surface covered with thin, scattered, bristle-shaped spines, about as long as the cephalis.

Dimensions.—Cephalis 0.02 diameter, thorax 0.2 long, 0.22 broad.

Habitat.—Central Pacific, Stations 271 to 274, surface.

22. Sethoconus anthocyrtis, n. sp. (Pl. [62], fig. 21).

Anthocyrtis sethoconus, Haeckel, 1879, Atlas, loc. cit.

Cephalis small, subspherical, with very small pores and numerous radial, bristle-shaped spines of the same length. Thorax wide, conical, about as long as broad, with parabolic outlines, its network very delicate, with subregular, hexagonal meshes. Surface with scarce, bristle-shaped spines (not represented in the figure). Mouth with a corona of numerous small, vertical spines.

Dimensions.—Cephalis 0.025 diameter, thorax 0.26 long, 0.24 broad.

Habitat.—North Pacific, Station 248, surface.

23. Sethoconus virgultus, n. sp.

Cladarachnium virgultum, Haeckel, 1881, Prodromus, p. 430.

Cephalis and thorax nearly of the same form and stricture as in Sethoconus facetus, but larger and wider, with the same delicate, hexagonal network (Pl. [55], fig. 1); it differs from the latter by the wider, more convex and campanulate form, but mainly by the armature of the surface, which is densely covered with thin, arborescent, bristle-shaped spines, irregularly branched, and four to eight times as large as the cephalis.

Dimensions.—Cephalis 0.02 diameter, thorax 0.32 long, 0.4 broad.

Habitat.—South Pacific, Station 288, surface.

24. Sethoconus setosus, n. sp.

Phlebarachnium setosum, Haeckel, 1881, Prodromus, p. 430.

Cephalis small, subspherical, with distinct collar septum, and the same network as the thorax, with numerous bristle-shaped horns of the same length. Thorax slenderly conical, twice as long as broad, with irregular, polygonal pores of little different sizes, and very thin bars. Surface covered with perpendicular, simple, bristle-shaped spines, about as long as the cephalis.

Dimensions.—Cephalis 0.02 diameter, thorax 0.12 long, 0.22 broad.

Habitat.—Central Pacific, Stations 266 to 272, surface.

25. Sethoconus venosus, n. sp. (Pl. [55], fig. 2).

Phlebarachnium venosum, Haeckel, 1881, Prodromus, p. 430, et Atlas, loc. cit.

Cephalis subspherical, with a stout prismatic horn twice the length, bearing three denticulate edges. The uppermost part of the thorax is supported by three diverging, radial beams arising from the deep collar stricture. Thorax wide, conical, nearly twice as long as broad, with slightly convex, thorny outlines; its delicate network is composed of very irregular, polygonal meshes of different sizes, separated by stronger bars, and of numerous very small polygonal pores separated by very thin bars inside the former. The central capsule of the figured specimen exhibited in the upper third of the thorax four large club-shaped lobes, which arose from a very small sphere enclosed in the cephalis and containing the nucleus.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.4 long, 0.3 broad.

Habitat.—Central Pacific, Station 271, surface.

Genus 573. Periarachnium,[[190]] Haeckel, 1881, Prodromus, p. 430.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with conical or campanulate, gradually dilated thorax, and widely open mouth. Primary lattice-shell enveloped by an external arachnoidal mantle. Cephalis with one or more horns.

The genus Periarachnium has been derived from those forms of the preceding Sethoconus, in which the conical thorax is covered with simple spines (Phlebarachnium) or branched spines (Cladarachnium). By communication of the branches of these spines a second outer shell is formed, which, like an arachnoidal mantle, envelops the inner primary shell.

1. Periarachnium periplectum, n. sp. (Pl. [55], fig. 11).

Cephalis hemispherical, separated from the thorax by a sharp collar stricture, from which arise three internal, diverging beams supporting its upper third. Thorax campanulate, conical, about as long as broad, with slightly convex outlines. The delicate lattice-work of the entire shell is double; the inner composed of subregular, hexagonal meshes; the outer of larger, irregular, polygonal meshes. The bars of the inner are much thicker than the thin threads of the outer. Both shells are connected by numerous bristle-shaped beams. The central capsule of the figured specimen exhibited in the upper part of the thorax three club-shaped lobes, which arose from a sphere enclosed in the cephalis and containing the nucleus.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.15 long, 0.12 broad.

Habitat.—Central Pacific, Station 271, surface.

Genus 574. Sethocephalus,[[191]] Haeckel, 1881, Prodromus, p. 430.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with discoidal, flatly expanded thorax. Cephalis large, without horn.

The genus Sethocephalus (formerly proposed under the name Platycryphalus) contains some few and rare Sethocorida, distinguished by the very large cephalis, the collar opening of which is wide open, not closed by cortinar beams, and surrounded by a very flat, nearly discoidal thorax, like the brim of a hat. It is possible that this peculiar genus has been derived from a Tricyrtid (Theocalyptra?) by loss of the original cephalis, and that the apparent large cephalis is the original thorax.

1. Sethocephalus eucecryphalus, n. sp. (Pl. [56], fig. 13).

Cephalis very large, campanulate-conical, with irregular, polygonal pores and thin bars. Thorax short, scarcely broader than the cephalis, beyond the sharp collar stricture expanded like the brim of a hat, with few rows of irregular, polygonal pores. (In the specimen figured the thorax was only half as broad as in another specimen found afterwards.)

Dimensions.—Cephalis 0.12 long, 0.09 broad; thorax 0.02 long, 0.12 broad.

Habitat.—South Pacific, Station 285, surface.

2. Sethocephalus platycryphalus, n. sp.

Platycryphalus sethodiscus, Haeckel, 1881, Prodromus, p. 430.

Cephalis large, hemispherical, with irregular square pores and thin bars. Thorax flatly conical, three to four times as broad as the cephalis, beyond the collar stricture expanded nearly discoidally, with a delicate network of small, subregular, hexagonal pores. (Similar in general form to Sethophormis aurelia, Pl. [55], fig. 3, but without any trace of collar beams or radial ribs.)

Dimensions.—Cephalis 0.04 long, 0.08 broad; thorax 0.04 long, 0.3 broad.

Habitat.—South Pacific, Station 289, surface.

Genus 575. Sethocyrtis,[[192]] n. gen.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with ovate or subcylindrical thorax, the mouth of which is constricted, simple, without prominent hyaline peristome. Cephalis with an apical horn.

The genus Sethocyrtis and the three following nearly allied genera differ from the three preceding genera of Sethocorida in the form of the thorax, which is not gradually dilated, conical, but cylindrical or ovate, with more or less constricted mouth. Sethocyrtis may be derived from Anthocyrtis by loss of the terminal feet. Its mouth is quite simple, without tubular or annular peristome.

1. Sethocyrtis oxycephalis, n. sp. (Pl. [62], fig. 9).

Shell rough, subconical, with slight collar stricture. Length of the two joints = 4 : 9, breadth = 3 : 8. Cephalis ovate, with a pyramidal horn of half the length. Thorax campanulate, with regular, circular pores, twice as broad as those of the cephalis. Mouth constricted, scarcely half as broad as the thorax.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 3000 fathoms.

2. Sethocyrtis cancrina, Haeckel.

Eucyrtidium cancrinum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. x. fig. 4.

Shell smooth, bottle-shaped, with obliterated collar stricture. Length of the two joints = 4 : 9, breadth = 2 : 7. Cephalis subcylindrical, with a stout conical horn of the same length, and sometimes a smaller accessory horn at its base. Thorax ovate, truncate, with regular, circular, quincuncial pores, twice as broad as those of the cephalis. Mouth little constricted, flat, nearly as broad as the thorax.

Dimensions.—Cephalis 0.04 long, 0.02 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Fossil in Barbados.

3. Sethocyrtis diomedis, n. sp.

Shell thorny, pear-shaped, with slight collar stricture. Length of the two joints = 3 : 16, breadth = 4 : 20. Cephalis hemispherical, with a conical horn of twice the length. Thorax inflate, ovate, truncate at both poles, with regular, circular pores, twice as broad as those of the thorax. Mouth constricted, flat, half as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.12 to 0.16 long, 0.16 to 0.2 broad.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.

4. Sethocyrtis menelai, n. sp.

Shell spiny, pear-shaped, with sharp collar stricture. Length of the two joints = 3 : 15, breadth = 4 : 18. Cephalis subspherical, with a large, cylindro-conical horn, about as long as the whole shell. Thorax inflate, subspherical, truncate, with large, irregular, roundish pores, four to six times as large as those of the cephalis. Mouth constricted, flat, one-third as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.15 long, 0.18 broad.

Habitat.—Fossil in Barbados.

5. Sethocyrtis subacuta, Haeckel.

Eucyrtidium subacutum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. fig. 18.

Shell smooth, pear-shaped, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with small, irregular pores and a rudimentary horn of half the length. Thorax ovate, with large, subregular, hexagonal pores and thin bars between them. Mouth constricted, flat, half as broad as the thorax, without prominent peristome.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Philippine Sea, depth 3300 fathoms (Ehrenberg).

6. Sethocyrtis pleuracantha, Haeckel.

Eucyrtidium pleuracanthum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. fig. 21.

Shell smooth, bottle-shaped, with distinct collar stricture. Length of the two joints = 2 : 4, breadth = 1 : 3. Cephalis slenderly ovate, with an excentric pyramidal horn of the same length. Thorax inflate, ovate, with irregular, roundish pores and thin bars between them. Mouth constricted, flat, half as broad as the thorax, without prominent peristome.

Dimensions.—Cephalis 0.04 long, 0.02 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Tropical Pacific, Stations 200, 225, 266, 274, &c., at various depths.

7. Sethocyrtis agamemnonis, n. sp. (Pl. [62], figs. 11, a, b).

Shell pear-shaped, rough, with sharp collar stricture. Length of the two joints = 2 : 10, breadth = 3 : 8. Cephalis subspherical, with very small pores and a small, pyramidal horn of half the length. Thorax inflate, ovate; in the uppermost part (beyond the collar stricture) with a ring of six to nine very large roundish pores, which are twice to four times as broad as the other irregular, roundish pores. (The shell is seen in fig. 11 from the apical pole, in fig. 11a with the cephalis, in fig. 11b without it, exhibiting the four central collar pores of the cortinar septum.) Mouth truncate, without prominent peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.1 long, 0.08 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

8. Sethocyrtis cassis, Haeckel.

Cornutella cassis, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 38.

Cyrtocalpis cassis, Haeckel, 1862, Monogr. d. Radiol., p. 287.

Shell pear-shaped, smooth, with obliterated collar stricture. Length of the two joints = 4 : 13, breadth = 3 : 12. Cephalis ovate, with a conical horn of half the length. Thorax inflate, ovate, with subregular, circular, quincuncial pores, twice to three times as broad as the bars. Mouth constricted, truncate, two-thirds as broad as the thorax, without prominent peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.13 long, 0.12 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Caltanisetta).

Genus 576. Sethocorys,[[193]] Haeckel, 1881, Prodromus, p. 430.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with ovate or sub-cylindrical thorax, the mouth of which is constricted and prolonged into a ring-like peristome. Cephalis with an apical horn.

The genus Sethocorys differs from the preceding Sethocyrtis, its ancestral form, in the form of the constricted mouth, which is prolonged into a prominent, hyaline, tubular, or annular peristome.

1. Sethocorys achillis, n. sp. (Pl. [62], fig. 8).

Shell rough, pear-shaped, with distinct collar stricture. Length of the two joints = 4 : 8, breadth = 3 : 8. Cephalis ovate, with a stout pyramidal horn of half the length. Thorax nearly spherical, with regular, circular, quincuncial pores of the same breadth as the cephalic pores. Mouth constricted, half as broad as the thorax, with a broad, smooth, striated peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Cosmopolitan; Mediterranean (Corfu), Atlantic, Indian, Pacific; many stations, at various depths.

2. Sethocorys patrocli, n. sp.

Shell thorny, pear-shaped, with slight collar stricture. Length of the two joints = 4 : 12, breadth = 3 : 10. Cephalis ovate, with a pyramidal horn of twice the length. Thorax ovate, truncate at both poles, with regular, circular pores, twice as broad as the cephalic pores. Mouth constricted, half as broad as the thorax, with a broad, smooth, prominent peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.12 long, 0.1 broad.

Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 3000 fathoms.

3. Sethocorys armadillo, Haeckel.

Eucyrtidium armadillo, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf ix. fig. 10.

Shell slenderly ovate, smooth, with deep collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 6. Cephalis ovate, at the apex thorny, with a conical horn of the same length. Thorax smooth, ovate, truncate, with small, regular, circular pores, disposed in from twelve to fifteen transverse rows of the same breadth as the cephalic pores. Mouth constricted, half as broad as the thorax, with a broad, hyaline, prominent peristome.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.06 broad.

Habitat.—Fossil in Barbados.

4. Sethocorys odysseus, n. sp. (Pl. [62], fig. 10).

Shell ovate, smooth, with obliterated collar stricture. Length of the two joints = 2 : 9, breadth = 4 : 8. Cephalis hemispherical, with a slender, conical horn of the same length. Thorax nearly spherical, with regular, circular pores, of the same breadth as the cephalic pores, quincuncially disposed. Mouth constricted, only one-third as broad as the thorax, with a broad, hyaline, prominent peristome.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Sethocorys amphora, Haeckel.

Lophophæna amphora, Stöhr, 1880, Palæontogr., vol. xxvi. p. 99, Taf. iii. fig. 11.

Shell ovate, mouth with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 4. Cephalis hemispherical, with a short conical horn of half the length. Thorax ovate, truncate, with small, regular, circular, quincuncial pores. Mouth constricted, half as broad as the thorax, with a narrow, prominent, hyaline peristome.

Dimensions.—Cephalis 0.015 long, 0.03 broad; thorax 0.07 long, 0.06 broad.

Habitat.—Fossil in Tertiary rocks of Sicily; Grotte (Stöhr).

6. Sethocorys ajacis, n. sp.

Shell slenderly ovate, smooth, without external collar stricture, but with an internal septum. Length of the two joints = 1 : 3, breadth = 1 : 2. Cephalis conical, with a large pyramidal horn of twice the length, and sometimes with a smaller accessory horn at its base; its pores scarce, irregular. Thorax ovate, truncate, hyaline, in the greater part without pores, in the smaller part with from two to four transverse rows of small, circular pores only. Mouth constricted, with a large cylindrical, tubular, hyaline peristome, half as long as the shell.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 577. Lophophæna,[[194]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with ovate or subcylindrical thorax, the mouth of which is either truncate or constricted. Cephalis armed with several large horns.

The genus Lophophæna differs from the nearly allied Sethocorys and Dictyocephalus only in the armature of the large cephalis, which bears a group of large horns, often arranged in a corona of radial spines. Sometimes these spines are connected by anastomosing branches (like Arachnocorys).

Subgenus 1. Lophophænula, Haeckel.

Definition.—Horns of the cephalis simple, free, radial spines, neither branched nor connected.

1. Lophophæna galea, Ehrenberg.

Lophophæna galea orci, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin p. 245.

Lophophæna apiculata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 11.

? Cornutella spiniceps, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 6.

Shell with slight collar stricture. Length of the two joints = 5 : 4, breadth = 5 : 6. Cephalis subglobular, with numerous bristle-shaped, radial spines, about as long as its radius. Thorax about the same size, truncate, conical, smooth, with wide open mouth. Pores in both joints of equal size, small, regular, circular.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.04 long, 0.06 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms; also fossil in Barbados.

3. Lophophæna radians, Ehrenberg.

Lophophæna radians, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 9.

? Lophophæna lynx, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. fig. 13.

Shell with slight collar stricture. Length of the two joints = 4 : 6, breadth = 4 : 5. Cephalis subglobular, with numerous, stout, conical, radial spines, about as long as its diameter. Thorax of about the same size, subcylindrical, smooth, truncate, with wide open mouth. Pores in both joints of equal size, small, regular, circular.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.06 long, 0.05 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; also fossil in Barbados.

3. Lophophæna liothorax, n. sp.

Shell with distinct collar stricture. Length of the two joints = 4 : 10, breadth = 4 : 8. Cephalis subglobular, with large, circular, hexagonally-framed pores, and with numerous stout, conical, radial spines, about as long as its diameter. Thorax twice as long, ovate, smooth, truncate, with little constricted mouth, and with irregular, roundish pores, of very different sizes.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.1 long, 0.08 broad.

Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

4. Lophophæna echinocephala, n. sp.

Shell with deep collar stricture. Length of the two joints = 4 : 8, breadth = 4 : 9. Cephalis subglobular, of the same shape as in the preceding species. Thorax thorny, inflate, nearly spherical, with a constricted mouth of half the breadth, and with irregular, roundish, double-contoured pores.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.08 long, 0.09 broad.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Subgenus 2. Lophophænoma, Haeckel.

Definition.—Horns of the cephalis connected by anastomosing branches.

5. Lophophæna circumtexta, Haeckel.

Lophophæna radians, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. viii. figs. 7, 8.

Shell with slight collar stricture. Length of the two joints = 4 : 5, breadth = 4 : 5. Cephalis subglobular, with numerous conical, radial spines, about as long as its diameter, and at equal distances from the surface, connected by anastomosing branches. Thorax nearly cylindrical, smooth, little dilated towards the truncate, wide open mouth. Pores subregular, circular.

Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.05 long, 0.05 broad.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.

Genus 578. Dictyocephalus,[[195]] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with ovate or subcylindrical thorax, the mouth of which is more or less constricted, either truncate or with a ring-like peristome. Cephalis rounded, without horn.

The genus Dictyocephalus has originated probably from Sethocorys by reduction and loss of the apical horn. The mouth is more or less constricted, either simple, truncate (Dictyocryphalus), or provided with a prominent, broad, hyaline, annular peristome (Dictyoprora).

Subgenus 1. Dictyoprora, Haeckel, 1881, Prodromus, p. 430.

Definition.—Mouth of the thorax constricted, with a prominent, ring-like or tubular, hyaline peristome.

1. Dictyocephalus amphora, n. sp. (Pl. [62], fig. 4).

Shell smooth, thick-walled, subovate, with slight collar stricture. Length of the two joints = 5 : 9, breadth = 6 : 8. Cephalis large, obtusely conical, with numerous oblique pore-canals. Thorax inflate, with six to eight transverse rows of roundish pores, increasing in size towards the base. Mouth constricted, one-third as broad as the thorax, with an internal diaphragm and a narrow hyaline peristome.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Stations 265 to 272, depth 2425 to 2925 fathoms.

2. Dictyocephalus urceolus, n. sp.

? Eucyrtidium Mongolfieri, Bury, 1862, Polycystins of Barbados, pl. v. fig. 2.

Shell smooth, thick-walled, urceolate, with obliterated collar stricture. Length of the two joints = 5 : 12, breadth = 4 : 10. Cephalis campanulate, with numerous oblique pore-canals. Thorax inflate, with five or six transverse rows of roundish pores of equal size. Mouth constricted, nearly half as broad as the thorax, with a broad hyaline peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.12 long, 0.1 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; also fossil in Barbados.

3. Dictyocephalus excellens, Haeckel.

Eucyrtidium excellens, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. x. fig. 2.

Shell annulate, thick-walled, urceolate, with slight collar stricture. Length of the two joints = 5 : 10, breadth = 4 : 7. Cephalis large, ovate-conical, with numerous oblique pore-canals. Thorax ovate, with ten to twelve transverse rows of regular, roundish pores, which are separated by prominent annular ribs. Mouth constricted, about half as broad as the thorax, with a broad hyaline peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.1 long, 0.07 broad.

Habitat.—Fossil in Barbados.

4. Dictyocephalus ocellatus, Haeckel.

Dictyocephalus ocellatus, Haeckel, 1862, Monogr. d. Radiol., p. 297.

? Eucyrtidium ocellatum, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 299.

Shell smooth, thick-walled, with deep collar stricture. Length of the two joints = 3 : 9, breadth = 4 : 7. Cephalis subspherical, with numerous oblique pore-canals. Thorax inflate, campanulate, hyaline, only with three or four remote transverse rows of circular, double-contoured pores of equal size. Mouth constricted, one-third as broad as the thorax, with a narrow hyaline annular peristome.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.07 broad.

Habitat.—North Atlantic, Greenland; Færöe Channel (Gulf Stream), John Murray.

5. Dictyocephalus crassiceps, Haeckel.

Eucyrtidium crassiceps, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xi. fig. 4.

Shell smooth, thick-walled, with sharp collar stricture. Length of the two joints = 4 : 6, breadth = 3 : 4. Cephalis ovate, in the upper part with scattered pores, in the lower part with one transverse row of pores. Thorax hyaline, subcylindrical, only with four or five remote transverse rows of small, circular pores. Mouth constricted, half as broad as the thorax, with a short hyaline peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.06 long, 0.04 broad.

Habitat.—Fossil in Barbados.

6. Dictyocephalus australis, n. sp. (Pl. [62], fig. 1).

Shell smooth, thick-walled, with slight collar stricture. Length of the two joints = 2 : 9, breadth = 3 : 6. Cephalis hemispherical, with few small pores. Thorax subcylindrical, with large, roundish, double-contoured pores, irregularly disposed. Mouth constricted, two-thirds as broad as the thorax, with a broad, hyaline peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.09 long, 0.06 broad.

Habitat.—East coast of Australia, Station 164, surface.

7. Dictyocephalus mediterraneus, n. sp. (Pl. [62], fig. 2).

Shell rough, thin-walled, with slight collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 8. Cephalis hemispherical, with small, circular pores. Thorax ovate, truncate, with much larger circular pores of different sizes and thin bars between them. Mouth little constricted, two-thirds as broad as the thorax, with a narrow, hyaline peristome.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.08 broad.

Habitat.—Mediterranean, Smyrna (Haeckel), surface.

8. Dictyocephalus papillosus, Haeckel.

Eucyrtidium papillosum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. fig. 10.

Shell thin-walled, papillate, with obliterated collar stricture. Length of the two joints = 2 : 7, breadth = 3 : 5. Cephalis hemispherical, with small, circular pores. Thorax slenderly ovate, with larger, subregular, circular pores, separated by oblique series of conical papillæ. Mouth with a broad, hyaline peristome (the "third articulus" of Ehrenberg), separated by a stricture from the little broader thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.05 broad.

Habitat.—Western Tropical Pacific (Philippine Sea), depth 3300 fathoms.

9. Dictyocephalus tabulatus, n. sp.

Shell thin-walled, papillate, with obliterated collar stricture. Length of the two joints = 2 : 10, breadth = 3 : 7. Cephalis hemispherical, with small, circular pores. Thorax slenderly ovate, truncate, with large, subregular, circular, hexagonally-framed pores. Mouth little constricted, nearly as broad as the thorax, with a broad, hyaline peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad, thorax 0.1 long, 0.07 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

10. Dictyocephalus reticulum, Haeckel.

Dictyocephalus reticulum, Haeckel, 1862, Monogr. d. Radiol., p. 297.

Eucyrtidium reticulum, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 300.

Shell thin-walled, smooth, with deep collar stricture. Length of the two joints = 2 : 8, breadth = 3 : 5. Cephalis subspherical, with small, circular pores. Thorax campanulate, with transverse rows of alternating square pores. Mouth little constricted, nearly as long as the thorax, with a narrow, prominent peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.05 broad.

Habitat.—Arctic Ocean, Greenland (Schaffner); Iceland (Krabbe).

11. Dictyocephalus ampulla, n. sp.

Shell thin-walled, smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, without pores, hyaline. Thorax inflate, subspherical, with scarce and small, widely-scattered, circular pores. Mouth constricted, only one-third as broad as the thorax, with a narrow, prominent peristome.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.08 long, 0.07 broad.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Subgenus 2. Dictyocryphalus, Haeckel, 1881, Prodromus, p. 430.

Definition.—Mouth of the thorax flat or truncate, without prominent ring-like peristome.

12. Dictyocephalus obtusus, Ehrenberg.

Dictyocephalus obtusus, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

Lophophæna obtusa, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 40.

Cornutella obtusa, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 877.

Dictyocephalus obtusus, Haeckel, 1862, Monogr. d. Radiol., p. 296.

Shell smooth, thick-walled, with distinct collar stricture. Length of the two joints = 5 : 6, breadth = 4 : 5. Cephalis ovate, little smaller than the subcylindrical thorax. Pores subregular, circular, of little different sizes. Mouth truncate, without ring-like peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.06 long, 0.05 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Caltanisetta), Grotte, &c.

13. Dictyocephalus globiceps, n. sp. (Pl. [62], fig. 7).

Shell rough, thin-walled, with distinct collar stricture. Length of the two joints = 6 : 8, breadth = 6 : 7. Cephalis subspherical, large, with circular, double-contoured pores. Thorax cylindrical, with irregular, roundish pores, the size of which, like the thickness of the wall, decreases gradually towards the truncate mouth, which has no ring-like peristome.

Dimensions.—Cephalis 0.06 long, 0.06 broad; thorax 0.08 long, 0.07 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

14. Dictyocephalus cavea, n. sp.

Shell rough, thin-walled, with slight collar stricture. Length of the two joints = 3 : 10, breadth = 5 : 7. Cephalis hemispherical, thorny, with numerous regular, circular pores. Thorax subcylindrical, with very large, circular, hexagonally-framed pores (in nine longitudinal alternating rows), three to five times as broad as the cephalic pores. Mouth truncate, wide open, without ring-like peristome.

Dimensions.—Cephalis 0.06 long, 0.1 broad; thorax 0.2 long, 0.14 broad.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

15. Dictyocephalus capito, Ehrenberg.

Dictyocephalus capito, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. vii. fig. 24.

Shell smooth, thin-walled, with sharp collar stricture. Length of the two joints = 7 : 9, breadth = 6 : 8. Cephalis ovate, with numerous irregular, roundish, densely-crowded pores. Thorax ovate, with very few widely-scattered, irregular, roundish pores (broken off in Ehrenberg's figure). Mouth truncate, little constricted, without ring-like peristome.

Dimensions.—Cephalis 0.07 long, 0.06 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Western Tropical Pacific (Philippine Sea) Station 206, depth 2100 fathoms.

16. Dictyocephalus hispidus, Ehrenberg.

Dictyocephalus hispidus, Ehrenberg, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, p. 289, Taf. v. fig. 18.

Shell rough, thin-walled, with deep collar stricture. Length of the two joints = 3 : 4, breadth = 3 : 5. Cephalis subspherical, spiny, with the same irregular, roundish pores as the funnel-shaped or nearly ovate thorax. Mouth truncate, little narrower than the thorax, without ring-like peristome.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.04 long, 0.05 broad.

Habitat.—Tropical Atlantic, Mexican Gulf (Ehrenberg); Station 338, depth 1990 fathoms.

Subfamily 2. Sethocapsida, Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethocyrtida with the basal mouth of the shell fenestrated (vel Dicyrtida eradiata clausa).

Genus 579. Sethocapsa,[[196]] Haeckel, 1881, Prodromus, p. 433 (sensu emendato).

Definition.—Sethocapsida (vel Dicyrtida eradiata clausa) with a free cephalis bearing an apical horn.

The genus Sethocapsa and the two following genera represent together the small subfamily of Sethocapsida, or those Dicyrtida in which the mouth of the thorax is closed, and no radial apophyses are present. Sethocapsa may be derived either from Lithopera by loss of the three radial rods, or from Sethocyrtis by closure of the mouth.

1. Sethocapsa pyriformis, n. sp. (Pl. [57], fig. 2).

Shell rough, pear-shaped, with slight collar stricture. Length of the two joints = 3 : 10, breadth = 3 : 8. Cephalis subspherical, with numerous small pores, and a short pyramidal or conical horn of half the length. Thorax ovate, with subregular, circular, quincuncial pores.

Dimensions.—Cephalis 0.03 diameter, thorax 0.1 long, 0.08 broad.

Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 3000 fathoms.

2. Sethocapsa lagena, Haeckel.

Lithopera lagena, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 4.

Shell smooth, pear-shaped, with sharp collar stricture. Length of the two joints = 3 : 8, breadth = 3 : 6. Cephalis pear-shaped, with few scarce pores, and a small conical horn of half the length. Thorax pear-shaped, with irregular, roundish pores. This species differs from the similar Lithopera lagena almost only in the complete absence of the three internal radial collar beams inside the thorax, and may be derived from it by their retrograde metamorphosis.

Dimensions.—Cephalis 0.03 diameter, thorax 0.08 long, 0.06 broad.

Habitat.—Fossil in Barbados.

3. Sethocapsa macroceros, n. sp.

Shell smooth, pear-shaped, with slight collar stricture. Length of the two joints = 2 : 11, breadth = 2 : 9. Cephalis subspherical, with small circular pores, and a very large, straight, pyramidal horn, of about the same length as the shell. Thorax ovate, with large, irregular, roundish pores, which are surrounded by polygonal frames.

Dimensions.—Cephalis 0.02 diameter, thorax 0.11 long, 0.09 broad.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

4. Sethocapsa nidus, Haeckel.

Lithopera nidus pendulus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 7.

Shell smooth, pear-shaped, with distinct collar stricture. Length of the two joints = 3 : 6, breadth = 3 : 5. Cephalis subspherical, with a large, straight, pyramidal horn of twice the length, and scarce small pores. Thorax ovate, also with very small and scarce pores.

Dimensions.—Cephalis 0.03 diameter, thorax 0.06 long, 0.05 broad.

Habitat.—Fossil in Barbados.

5. Sethocapsa bulla, n. sp.

Shell spiny, with slight collar stricture. Length of the two joints = 3 : 12, breadth = 4 : 12. Cephalis hemispherical, with small, scarce pores, and a conical horn of the same length. Thorax nearly spherical, with large, subregular, circular, quincuncial pores, twice as broad as the bars.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.12 long, 0.12 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms; fossil in Barbados.

6. Sethocapsa ampulla, n. sp.

Shell papillate, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis hemispherical, hyaline, without pores, with a large pyramidal horn of twice the length. Thorax nearly spherical, with large, irregular, roundish, lobulated pores.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.15 long, 0.15 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

7. Sethocapsa staurocephala, Haeckel.

? Lithopera oxystauros, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 6.

? Lithopera amblystauros, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 5.

Shell smooth, with slight collar stricture. Length of the two joints = 3 : 4, breadth = 3 : 4. Cephalis large, ovate, with a conical horn of the same length, small scarce pores, and an internal frontal septum, composed of two crossed beams, a vertical and a horizontal. Thorax little larger than the cephalis, ovate, with irregular, small and scarce pores. (The two figures of Ehrenberg are either incomplete—in Lithopera amblystauros, the cephalic horn, and in Lithopera oxystauros, the basal part of the thorax, being broken off—or they belong to different Botryodea).

Dimensions.—Cephalis 0.03 diameter, thorax 0.04 diameter.

Habitat.—Fossil in Barbados.

Genus 580. Dicolocapsa,[[197]] Haeckel, 1881, Prodromus, p. 433 (sensu emendato).

Definition.—Sethocapsida (vel Dicyrtida eradiata clausa) with a free cephalis, without apical horn.

The genus Dicolocapsa differs from the preceding Sethocapsa in the loss of the apical horn, and therefore bears to it the same relation that Dictyocephalus does to Sethocyrtis.

1. Dicolocapsa microcephala, n. sp. (Pl. [57], fig. 1).

Shell smooth, thin-walled, with distinct collar stricture. Cephalis small, subspherical, with small, crowded pores. Length of the two joints = 1 : 3, breadth = 1 : 3. Thorax also nearly spherical, three times as large as the cephalis, with small, irregularly scattered, circular pores, and much broader bars.

Dimensions.—Cephalis 0.03 diameter, thorax 0.09 diameter.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Dicolocapsa megacephala, n. sp.

Shell smooth, thin-walled, with sharp collar stricture. Cephalis large, conical, obtuse. Length of the two joints = 5 : 9, breadth = 6 : 8. Thorax ovate, truncate, with hemispherical base. Pores of both joints equal, subregular, circular, about as broad as the bars.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Dicolocapsa platycephala, n. sp.

Shell papillate, thick-walled, with slight collar stricture. Cephalis flat, hemispherical, hyaline, without pores (or with few small pores). Length of the two joints = 2 : 11, breadth = 4 : 9. Thorax ovate, with small, regular, circular pores, half as broad as the bars.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.11 long, 0.09 broad.

Habitat.—Fossil in Barbados.

Genus 581. Cryptocapsa,[[198]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethocapsida (vel Dicyrtida eradiata clausa) with a cephalis hidden in the thorax, without apical horn.

The genus Cryptocapsa differs from the preceding Dicolocapsa, its ancestral form, in the peculiar shape of the cephalis, which is nearly perfectly enclosed in the upper part of the inflated thorax. It has, therefore, to the latter the same relation as Carpocanium bears to Anthocyrtis.

1. Cryptocapsa bacca, n. sp.

Cephalis spherical, with small circular pores enclosed in the upper part of the thorax, which is ovate, smooth, and exhibits regular, circular pores, about as broad as the bars.

Dimensions.—Cephalis 0.03 diameter, thorax 0.15 long, 0.12 broad.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Cryptocapsa pila, n. sp.

Cephalis spherical, with few small pores, enclosed in the upper part of the thorax, which is pear-shaped, spiny, and exhibits subregular, hexagonal pores, three times as broad as the bars. From each hexagon corner a small thorn arises.

Dimensions.—Cephalis 0.04 diameter, thorax 0.25 long, 0.17 broad.

Habitat.—Central Pacific, Station 269, depth 2900 fathoms.