Section I. MONOCYRTIDA, Haeckel, 1862, Monogr. d. Radiol., pp. 280, 281.

Definition.—Cyrtoidea monothalamia, with simple, not jointed shell (or cephalis), without transverse constrictions.

Synopsis of the three Families and six Subfamilies of Monocyrtida.

Family LIX. Tripocalpida.

Three radial apophyses.

Mouth open,1. Archipilida.
Mouth closed,2. Archiperida.

Family LX. Phænocalpida.

Numerous radial apophyses.

Mouth open,3. Archiphormida.
Mouth closed,4. Archiphænida.

Family LXI. Cyrtocalpida.

No radial apophyses.

Mouth open,5. Archicorida.
Mouth closed,6. Archicapsida.

Family LIX. Tripocalpida.

Three radial apophyses.

Mouth open,
1. Archipilida.
Mouth closed,
2. Archiperida.

Family LX. Phænocalpida.

Numerous radial apophyses.

Mouth open,
3. Archiphormida.
Mouth closed,
4. Archiphænida.

Family LXI. Cyrtocalpida.

No radial apophyses.

Mouth open,
5. Archicorida.
Mouth closed,
6. Archicapsida.

Family LIX. Tripocalpida, n. fam.

Archipilida et Archiperida, Haeckel, 1881, Prodromus, pp. 427, 429.

Definition.—Monocyrtida triradiata. (Cyrtoidea with a simple, not jointed shell, representing a simple cephalis, with three radial apophyses.)

The family Tripocalpida, composed of the Archipilida and Archiperida of my Prodromus, comprises those Cyrtoidea in which the lattice-shell is quite simple, without transverse constriction, and bears three radial apophyses. The two subfamilies differ in the shape of the basal mouth, which in the Archipilida is a simple wide opening, in the Archiperida closed by a lattice-plate; the former are here divided into eight, the latter into seven different genera.

Only three species of this family were hitherto described, all three belonging to the Archipilida, viz., (1) Tripocalpis galea (fossil in Barbados, figured by Ehrenberg, 1875, as Halicalyptra galea), (2) Tripodiscium campanula (fossil in Sicily, figured by Stöhr, 1880, as Carpocanium); and (3) Tridictyopus elegans, of which Richard Hertwig gave an excellent description in 1879, with an accurate figure of the central capsule. All the other species of the family (seventy) are new.

The shell in the majority of Tripocalpida is ovate or campanulate, sometimes conical or three-sided pyramidal. Three radial apophyses are constantly distinct, either three lateral wings or three terminal feet; these are usually solid spines, rarely lattice-plates. The top of the shell usually bears an apical horn, rarely two or more horns; often the horn is wanting. The lattice-work of the shell is very various in the different species, and often of a remarkable structure (Pl. [51], figs. 6-8; Pl. [98], figs. 4-8). The cavity of the shell is in all Archipilida, and in a part of the Archiperida (Peridium, Archipera, Archibursa) quite simple. In the other part of the Archiperida, however, constituting the peculiar group of Euscenida (genera 504-507), a vertical columella arises in the centre of the basal plate, and is prolonged upwards in the apical horn; this columella is either simple (Euscenium, Archiscenium) or branched (Cladoscenium, Pteroscenium); in the latter case the ascending branches are disposed in triradiate verticils and are inserted on the inner face of the shell (compare Pl. [53], figs. 11-16, and Pl. [98], figs. 1-4).

The phylogenetic origin of the Tripocalpida may be very divergent, and their morphological affinity to the other Nassellaria is a very complicated problem. The Euscenida (genera 504-507) may be derived directly from the Plagonida (Plagoniscus) or Plectanida (Plectaniscus). The Archibursida (genera 508-510) however, manifest a closer affinity to the Tripospyrida, and may be derived from them by reduction of the sagittal ring and constriction. In these two groups of Archiperida the shell may be regarded as a true cephalis. In the Archipilida, however, where the shell has a wide basal opening and the three radial ribs arise originally from the base of the apical horn, the shell itself may correspond to the thorax of the Dicyrtida, and may be derived from these by loss of the cephalis. This is the more probable, as sometimes a small remnant of the reduced cephalis is preserved (Pl. [98], fig. 8). None of these difficult questions can be answered until a much closer morphological knowledge of the Tripocalpida is acquired.

Synopsis of the Genera of Tripocalpida.

I. Subfamily Archipilida.

Basal mouth of the shell a simple wide opening.

Shell with three lateral ribs or wings, with or without terminal feet.Three terminal feet.Apex with a horn,496. Tripocalpis.
No apical horn,497. Tripodonium.
Six to nine or more terminal feet.No apical horn,498. Tripterocalpis.
No terminal feet.Apex with a horn,499. Trissopilium.
No apical horn,500. Archipilium.
Shell without lateral ribs or wings but with three terminal feet.Feet simple or branched, not latticed.Apex with a horn,501. Tripilidium.
No apical horn,502. Tripodiscium.
Feet latticed.Apex with a horn,503. Tridictyopus.

II. Subfamily Archiperida.

Basal mouth of the shell closed by a lattice-plate.

Shell in its axis with a free (simple or branched) internal columella, prolonged into an apical horn.Shell with three free feet, without lateral lattice-wings.Columella simple,504. Euscenium.
Columella branched,505. Cladoscenium.
Shell with three lateral lattice-wings, connecting the three feet with the horn.Columella simple,506. Archiscenium.
Columella branched,507. Pteroscenium.
Shell with simple cavity, without free columella. Three free basal feet.One apical horn,508. Peridium.
Two or more horns,509. Archipera.
No apical horn,510. Archibursa.

I. Subfamily Archipilida.

Basal mouth of the shell a simple wide opening.

Shell with three lateral ribs or wings, with or without terminal feet.
Three terminal feet.
Apex with a horn,
496. Tripocalpis.
No apical horn,
497. Tripodonium.
Six to nine or more terminal feet.
No apical horn,
498. Tripterocalpis.
No terminal feet.
Apex with a horn,
499. Trissopilium.
No apical horn,
500. Archipilium.
Shell without lateral ribs or wings but with three terminal feet.
Feet simple or branched, not latticed.
Apex with a horn,
501. Tripilidium.
No apical horn,
502. Tripodiscium.
Feet latticed.
Apex with a horn,
503. Tridictyopus.

II. Subfamily Archiperida.

Basal mouth of the shell closed by a lattice-plate.

Shell in its axis with a free (simple or branched) internal columella, prolonged into an apical horn.
Shell with three free feet, without lateral lattice-wings.
Columella simple,
504. Euscenium.
Columella branched,
505. Cladoscenium.
Shell with three lateral lattice-wings, connecting the three feet with the horn.
Columella simple,
506. Archiscenium.
Columella branched,
507. Pteroscenium.
Shell with simple cavity, without free columella. Three free basal feet.
One apical horn,
508. Peridium.
Two or more horns,
509. Archipera.
No apical horn,
510. Archibursa.

Subfamily 1. Archipilida, Haeckel, 1881, Prodromus, p. 427.

Definition.—Tripocalpida with the basal mouth of the shell open (vel Monocyrtida triradiata aperta).

Genus 496. Tripocalpis,[[113]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral ribs prolonged into three terminal feet. Apex with a horn.

The genus Tripocalpis opens the series of Archipilida, or of those Monocyrtida in which the monothalamous shell exhibits a distinct triradial structure, and a simple open mouth, without cortinar lattice. Tripocalpis is probably the most primordial of the Archipilida, and has three lateral ribs, which are prolonged into three free terminal feet, and connected in the apex of the pyramidal or campanulate shell with the apical horn. It may probably be derived from Dictyophimus by loss of the cephalis. The central capsule is simple, spherical, or ellipsoidal.

1. Tripocalpis plectaniscus, n. sp.

Shell three-sided pyramidal, smooth, about as long as broad, with irregular polygonal pores and thin bars. Apical horn stout, three-sided pyramidal, about as long as the shell. From the three edges of its base arise three prominent straight radial ribs, which are prolonged into three large divergent feet, of equal size and the same form as the horn.

Dimensions.—Shell 0.1 diameter, horn and feet 0.12.

Habitat.—Tropical Pacific (Philippine Sea), Station 206, depth 2100 fathoms.

2. Tripocalpis galea, Haeckel.

Halicalyptra galea, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. ii. fig. 10.

Shell campanulate, rough, about as long as broad, with irregular roundish pores and thick bars. Apical horn stout, three-sided pyramidal, scarcely one-fourth as long as the shell. Beyond its base there arise three prominent, slightly curved lateral ribs, which are prolonged into three pyramidal, slightly divergent stout feet, somewhat shorter than the shell.

Dimensions.—Shell 0.08 to 0.09 diameter, horn 0.02, feet 0.07.

Habitat.—Fossil in Barbados.

3. Tripocalpis tricostata, n. sp.

Shell ovate campanulate, one and a half times as long as broad, with regular circular pores, disposed in alternate longitudinal rows. Apical horn three-sided pyramidal, stout, half as long as the shell. In the middle of the shell there arise three wing-like lateral ribs, which are prolonged into three broad, slightly curved, divergent terminal feet.

Dimensions.—Shell 0.12 long, 0.08 broad, horn and feet 0.06 to 0.08.

Habitat.—Fossil in Barbados.

4. Tripocalpis triserrata, n. sp. (Pl. [51], fig. 6).

Shell ovate, nearly twice as long as broad. The three sides of the shell, between the three large ribs, are provided each with nine delicate parallel, longitudinal, slightly curved ribs, alternating with ten longitudinal rows of regular circular pores about as broad as the bars. Apical horn short and broad, three-sided pyramidal; from the three edges of its base there arise three wing-like serrate main ribs, which are prolonged into three short pyramidal terminal feet.

Dimensions.—Shell 0.12 long, 0.07 broad, horn and feet 0.01.

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

5. Tripocalpis cortinaris, n. sp. (Pl. [97], fig. 3).

Shell hemispherical, one and a half times as broad as long, with regular, circular, hexagonally framed pores, Apical horn stout, three-sided pyramidal, with three serrate edges. From the base of the latter arise three strongly dentate and curved lateral ribs, with recurved teeth, and these are prolonged into the serrate convex edge of the three basal feet, which are crescentic and twice as long as the shell.

Dimensions.—Shell 0.07 long, 0.1 broad; horn 0.06 long, feet 0.14 long.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

Genus 497. Tripodonium,[[114]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral ribs prolonged into three terminal feet. Apex without horn.

The genus Tripodonium differs from the preceding Tripocalpis, its probable ancestral form, only in the loss of the apical horn (already very small in some forms of the latter). It bears therefore to the latter the same relation that Sethopilium does to Dictyophimus.

1. Tripodonium campanulatum, n. sp.

Shell campanulate, somewhat broader than high, with regular circular pores, twice as broad as the bars. Three broad lateral wings, lamellar, triangular, are prolonged over the peristome into three short triangular lamellar feet one-fourth as long as the shell.

Dimensions.—Shell 0.08 long, 0.09 broad; feet 0.02 long.

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

2. Tripodonium ovatum, n. sp.

Shell ovate, one and one-third times as long as broad, with numerous and small circular pores, scarcely as broad as the bars. Three prominent longitudinal ribs, arising in the lower half of the shell-wall, are prolonged into three divergent conical curved feet, about half as long as the shell.

Dimensions.—Shell 0.12 long, 0.09 broad; feet 0.06 long.

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

Genus 498. Tripterocalpis,[[115]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral wings and a peristomial corona of numerous terminal feet. Shell ovate, with constricted mouth, without apical horn.

The genus Tripterocalpis is distinguished from the other Archipilida by the remarkable combination of three lateral wings and of numerous (six to nine or more) terminal feet. It may be derived directly from the preceding Tripocalpis by multiplication of the terminal feet. These are sometimes obliquely directed. The central capsule is ellipsoidal or ovate, and fills up the greater part of the shell.

1. Tripterocalpis phylloptera, n. sp. (Pl. [51], fig. 1).

Shell slender, ovate, nearly twice as long as broad. Pores circular, of different sizes and at unequal distances. Along the lower half of the shell there arise three broad triangular lamellar wings. Peristome with twelve conical, nearly parallel and vertical feet, about one-sixth as long as the shell.

Dimensions.—Shell 0.2 long, 0.12 broad; wings 0.1 long, feet 0.03 long.

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

2. Tripterocalpis conoptera, n. sp. (Pl. [51], fig. 2).

Shell ovate, nearly as broad as long. Pores regular, circular, quincuncial, twice as broad as the bars. In the middle of the shell there arise three conical, smooth, divergent wings, about half as long as the shell. Peristome with six short triangular, oblique, convergent feet.

Dimensions.—Shell 0.16 long, 0.14 broad; wings 0.09 long; feet 0.02 long.

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

3. Tripterocalpis ogmoptera, n. sp. (Pl. [51], figs. 3-5).

Shell ovate, nearly as broad as long. Pores small and numerous, circular or roundish, partly confluent, double-contoured (fig. 4). In the middle of the shell there arise three very large conical divergent wings, which are longitudinally striped and longer than half the shell. Peristome with nine short triangular, oblique, convergent feet.

Dimensions.—Shell 0.18 long, 0.16 broad; wings 0.12 long, feet 0.02 long.

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

Genus 499. Trissopilium,[[116]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral ribs or wings. Mouth smooth, without terminal feet. Apex with a horn.

The genus Trissopilium and the following nearly allied Archipilium differ from the other Archipilida in the absence of terminal feet, the peristome being quite simple, and truncate. But there are three lateral wings, arising either from the apex or from the lateral sides of the monothalamous shell. Trissopilium may perhaps be derived from Lithomelissa by reduction of the cephalis.

1. Trissopilium tetraplecta, n. sp.

Shell in the upper half three-sided pyramidal, in the lower half inversely hemispherical, of equal length and breadth. Pores irregular, roundish, in the upper half larger. From the apex there diverge four equal, straight and stout, three-sided pyramidal spines, one of which is vertically ascending (the horn), the three others obliquely descending (the wings). The distal half of the latter is free, whilst the proximal half forms three ribs, enclosed in the shell-wall. Mouth constricted, half as broad as the shell.

Dimensions.—Shell 0.08 long and broad, horn and wings 0.1 long.

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

2. Trissopilium lithomelissa, n. sp.

Shell ovate, one and one-third times as long as broad. Pores circular, of different sizes, small and numerous. Apical horn very large, straight, cylindrical, vertical, longer than the shell. Three lateral wings shorter, arising from the middle of the shell, conical, curved, divergent. Mouth truncate, two-thirds as broad as the shell.

Dimensions.—Shell 0.11 long, 0.08 broad; horn 0.13 long, wings 0.09 long.

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

Genus 500. Archipilium,[[117]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral ribs or wings. Mouth truncate, without terminal feet. Apex without horn.

The genus Archipilium differs from the nearly allied Trissopilium, its probable ancestral form, in the absence of the apical horn. The three lateral wings of the ovate shell are stout spines. It may also be derived from the similar Sethopilium by reduction and loss of the cephalis.

1. Archipilium orthopterum, n. sp. (Pl. [98], fig. 7).

Shell ovate, smooth, nearly cylindrical, scarcely broader than the truncate, widely open mouth. Pores numerous, irregular, roundish, of very different sizes. Three lateral wings arising from the middle zone, twice as long as the shell, straight, divergent, stout, cylindrical, longitudinally striped.

Dimensions.—Shell 0.08 long, 0.06 broad; wings 0.15 long.

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

2. Archipilium sigmopterum, n. sp.

Shell ovate, smooth, nearly campanulate, of equal length and breadth, one and one-third times as broad as the truncate, slightly constricted mouth. Pores scarce, irregularly formed and scattered, of very different sizes. Three lateral wings, stout, prismatic, about as long as the shell widely divergent and S-shaped, curved.

Dimensions.—Shell 0.08 diameter, wings 0.08 long.

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

3. Archipilium cyrtopterum, n. sp.

Shell ovate, rough, twice as broad as the constricted mouth. Pores small and numerous, subregular, circular, smaller than the bars. Three lateral wings cylindrical, crescentic, in the upper half divergent, in the lower convergent, one and one-half times as long as the shell.

Dimensions.—Shell 0.09 long, 0.07 broad; wings 0.14 long.

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

Genus 501. Tripilidium,[[118]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) without lateral ribs, with three simple or branched terminal feet and an apical horn.

The genus Tripilidium differs from Tripodonium in the absence of the three lateral ribs, and may be derived either from this ancestral form, or directly from Tripospyris (by loss of the sagittal ring and constriction); perhaps also from Lychnocanium (by reduction of the cephalis). We distinguish as two subgenera, Tristylocorys (with simple feet) and Tripodocorys (with branched feet).

Subgenus 1. Tristylocorys, Haeckel.

Definition.—Feet simple, not branched.

1. Tripilidium cortina, n. sp.

Shell campanulate, rough, about as long as broad. Pores subregular, circular, larger in the middle zone, twice to three times as broad as the bars. Mouth constricted, half as broad as the shell. Apical horn straight and stout, three-sided pyramidal, about as long as the shell. Three feet divergent, slightly S-shaped, curved, somewhat longer the the shell.

Dimensions.—Shell 0.1 diameter, horn 0.09 long, feet 0.13 long.

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

2. Tripilidium hemisphæricum, n. sp.

Shell hemispherical, smooth, nearly twice as broad as long. Pores large, with thin bars, irregular, roundish, of very different sizes. Mouth wide open. Apical horn conical, half as long as the shell. Three feet slender cylindrical, widely divergent, curved, nearly twice as long as the shell.

Dimensions.—Shell 0.08 long, 0.14 broad; horn 0.05 long, feet 0.15 long.

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

3. Tripilidium lychnocanium, n. sp.

Shell hemispherical, thorny, one and a half times as broad as long. Pores regular, circular, hexagonally framed, as broad as the bars. Mouth slightly constricted. Apical horn stout and short, three-sided pyramidal. Three feet cylindrical, straight, divergent, twice to three times as long as the shell. (Similar to Lychnocanium favosum, Pl. [61], fig. 6, perhaps derived from it by reduction of the cephalis.)

Dimensions.—Shell 0.08 long, 0.12 broad; horn 0.02 long, feet 0.2 long.

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

4. Tripilidium ovatum, n. sp.

Shell ovate, smooth, one and one half times as long as broad. Pores regular, circular, as broad as the bars. Mouth constricted, half as broad as the shell. Horn short, conical. Three feet conical, curved, convergent, scarcely one-third as long as the shell.

Dimensions.—Shell 0.15 long, 0.11 broad; horn 0.02 long, feet 0.04 long.

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

5. Tripilidium clavatum, n. sp.

Shell nearly spherical, tuberculate, a little broader than long. Pores regular, circular, as broad as the bars. Mouth constricted, half as broad as the shell. Apical feet and the three divergent feet of equal size and similar form, about as long as the shell, straight, in the basal half smooth, cylindrical, in the distal half club-shaped, dimpled. (Very similar to Tripospyris conifera and Tripospyris eucolpos, Pl. [84], figs. 7 and 4; but the spherical shell exhibits no trace of sagittal ring or constriction, and the simple shell-cavity has a wide open mouth, and is not closed by a basal plate.)

Dimensions.—Shell 0.1 diameter, horn and feet 0.08 to 0.09 long.

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

6. Tripilidium costatum, n. sp. (Pl. [98], figs. 8, 8a, 8b).

Shell ovate, spinulate and costate, nearly twice as broad as long. Surface with fifteen to twenty prominent longitudinal ribs, which are convergent towards each pole and elegantly denticulate. The deep furrows between them are divided by delicate, parallel, transverse ribs into numerous short and broad dimples (thirty to forty in each furrow); each dimple contains a small pore, like a transverse fissure. The apex bears a short and stout, three-sided pyramidal horn, the hollow base of which is closed by a small cortinar septum with three collar pores (fig. 8b). This seems to indicate a rudimentary cephalis and the derivation of this species from Lychnocanium (Pl. [61]). Peristome constricted, only one-fourth as broad as the shell, with three short, conical, nearly vertical feet. The central capsule (fig. 8a) in the specimen examined was well preserved, hemispherical, not lobate, and filled up the upper half of the shell-cavity (beyond the rudiment of the cortinar septum).

Dimensions.—Shell 0.2 long, 0.12 broad; horn 0.01 long, feet 0.02 long.

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

7. Tripilidium elongatum, n. sp.

Shell elongate, smooth, nearly cylindrical, in the upper third conical. Pores small and numerous, regular, circular, half as broad as the bars, disposed in about thirty longitudinal alternating rows. Peristome scarcely constricted. The apical horn and the three parallel feet are of equal size and similar form, straight, conical, one-sixth as long as the shell.

Dimensions.—Shell 0.12 long, 0.06 broad; horn and feet 0.02 long.

Habitat.—Fossil in Barbados.

Subgenus 2. Tripodocorys, Haeckel, 1881, Prodromus, p. 428.

Definition.—Feet forked or branched.

8. Tripilidium dichopodium, n. sp.

Shell hemispherical, nearly twice as broad as long, smooth. Pores irregular, roundish, twice to four times as broad as the bars. Mouth wide open. Apical horn spindle-shaped, half as long as the shell. Three feet cylindrical, nearly straight and parallel, as long as the shell, forked at the distal end. (Exhibits an external similarity to Tripospyris semantis, Pl. [84], fig. 2, but has no trace of sagittal ring and constriction, and the simple shell-cavity has a wide open mouth.)

Dimensions.—0.06 long, 0.1 broad; horn 0.03 long, feet 0.07 long.

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

9. Tripilidium cladopodium, n. sp.

Shell campanulate, rough, about as long as broad. Pores subregular, circular, as broad as the bars. Mouth slightly constricted. Apical horn and three divergent feet of nearly equal size and form, three-sided prismatic, straight and stout, irregularly dentate and branched, somewhat longer than the shell.

Dimensions.—Shell 0.08 diameter; horn and feet 0.1 to 0.12 long.

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

Genus 502. Tripodiscium,[[119]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) without lateral ribs and apical horn, with three simple or branched terminal feet.

The genus Tripodiscium may be derived either from the preceding Tripilidium by loss of the apical horn, or from the nearly related Tristylospyris by loss of the sagittal ring and constriction. Some forms of the latter genus can scarcely be distinguished from similar species of the former.

Subgenus 1. Tripodiscinus, Haeckel.

Definition.—Feet simple, not branched nor forked.

1. Tripodiscium tristylospyris, n. sp.

Shell subspherical, with regular, circular pores, twice as broad as the bars. Mouth constricted, half as broad as the shell, with three short spindle-shaped feet, which are nearly parallel and vertical, half as long as the shell. (Similar to Tristylospyris scaphipes, Pl. [84], fig. 13, but without sagittal ring and constriction.)

Dimensions.—Shell 0.08 long, 0.07 broad; feet 0.04 long.

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

2. Tripodiscium ovatum, n. sp.

Shell ovate, rough, nearly as broad as long. Pores regular circular, double-contoured, twice as broad as the bars. Mouth constricted, one-third as broad as the shell, with three convergent short triangular feet.

Dimensions.—Shell 0.1 long, 0.09 broad; feet 0.02 long.

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

3. Tripodiscium clavatum, n. sp.

Shell ovate, smooth, one and a half times as long as broad. Pores irregular roundish, of different sizes. Mouth constricted, two-thirds as broad as the shell, with three divergent, straight club-shaped feet, nearly as long as the shell.

Dimensions.—Shell 0.12 long, 0.08 broad; feet 0.1 long.

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

4. Tripodiscium campanula, Haeckel.

Carpocanium campanula, Stöhr, 1880, Palæontogr., vol. xxvi. p. 96, Taf. iii. fig. 9.

Shell campanulate or subspherical, smooth, about as long as broad. Pores small, regular circular, as broad as the bars. Mouth constricted, about half as broad as the shell, with three short conical descending feet.

Dimensions.—Shell 0.06 long, 0.05 broad; feet 0.02 long.

Habitat.—North Pacific, Station 244, depth 2900 fathoms; fossil in Sicily.

Subgenus 2. Tripodisculus, Haeckel.

Definition.—Feet branched or forked.

5. Tripodiscium furcatum, n. sp.

Shell ovate, rough, nearly as broad as long. Pores subregular, circular, twice as broad as the bars. Mouth constricted, two-thirds as broad as the shell, with three divergent parallel and vertical feet, which are as long as the shell, and forked at the distal end.

Dimensions.—Shell 0.09 long, 0.08 broad; feet 0.07 long.

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

6. Tripodiscium ramosum, n. sp.

Shell ovate, tuberculate, nearly as broad as long. Pores irregular, roundish, of very different sizes. Mouth constricted, half as broad as the shell, with three large, divergent, irregularly branched feet, nearly twice as long as the shell. (Similar to Tristylospyris ramosa, Pl. [52], fig. 23, but without sagittal ring and constriction.)

Dimensions.—Shell 0.07 long, 0.06 broad; feet 0.15 long.

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

7. Tripodiscium sphærocephalum, n. sp. (Pl. [52], fig. 21).

Shell subspherical, rough, with circular pores of different sizes. Mouth constricted, circular, simple, two-thirds as broad as the shell, with three large divergent feet, which are three-sided prismatic, irregularly branched, and twice as long as the shell.

Dimensions.—Shell 0.07 long, 0.08 broad; feet 0.12 long.

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

Genus 503. Tridictyopus,[[120]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three latticed terminal feet. Shell ovate or subconical, with an apical horn.

The genus Tridictyopus differs from the nearly allied Tripilidium in the possession of three large fenestrated shovel-shaped feet, forming direct prolongations of the large conical shell. The lattice work exhibits a peculiar elegant structure recurring in the similar, perhaps nearly related, Cephalospyris (Pl. [83], fig. 10; Pl. [96], fig. 28). The central capsule is large, ellipsoidal or ovate, and fills up the greater part of the shell cavity (compare R. Hertwig, 1879, loc. cit., p. 75).

1. Tridictyopus vatillum, n. sp. (Pl. [51], fig. 8).

Shell campanulate, about as long as broad (excluding horn and feet). Pores irregular, polygonal, in the middle part more regular, triangular. Horn short and stout, three-sided pyramidal. Three feet large, triangular, shovel-shaped, about half as long as the shell.

Dimensions.—Shell 0.14 long, 0.15 broad.

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

2. Tridictyopus conulus, n. sp. (Pl. [51], fig. 7).

Shell campanulate conical, about one and a half times as long as broad (excluding horn and feet). Pores mostly triangular, disposed in subregular hexagonal figures, which are separated by bands of smaller irregular polygonal pores. Horn short and stout, three-sided pyramidal. Three feet triangular shovel-shaped, convergent, about one-sixth as long as the shell.

Dimensions.—Shell 0.3 long, 0.2 broad; horn 0.04 long, feet 0.05 long.

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

3. Tridictyopus elegans, R. Hertwig.

Tridictyopus elegans, R. Hertwig, 1879, Organismus d. Radiol., p. 75, Taf. vii. fig. 3, 3a, 3b.

Shell slender, conical, campanulate, about twice as long as broad (excluding horn and feet). Most pores subregular triangular, with some irregular polygonal ones intermingled. The horn in the two observed specimens was broken off, together with the conical apex of the shell. Three feet triangular shovel-shaped, about one-sixth as long as the shell.

Dimensions.—Shell 0.3 long, 0.15 broad; feet 0.05 long.

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

Subfamily 2. Archiperida, Haeckel, 1881, p. 429.

Definition.—Tripocalpida with the basal mouth of the shell fenestrated (vel Monocyrtida triradiata clausa).

Genus 504. Euscenium,[[121]] n. gen.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) with a free simple internal columella, prolonged into an apical horn. Three basal feet free, without lateral wings.

The genus Euscenium and the three following nearly allied genera form together the remarkable small group of Euscenida, probably one of the oldest and most primitive of all Cyrtoidea, and perhaps the common root of this suborder, arising directly from the Plectoidea. The simple skeleton is composed of four radial beams united in one point (the cortinar centrum). Three beams are directed downwards, and form three divergent basal feet; the fourth beam is directed upwards and represents an apical horn; its basal part is enclosed as "columella" in the cavity of the simple shell, the lattice-work of which connects the four spines (compare above, Plectaniscus, p. 924). In the genus Euscenium, the simplest of all, the columella is simple, and the three feet also simple, without wings.

Subgenus 1. Euscenarium, Haeckel.

Definition.—Three feet simple, not branched.

1. Euscenium plectaniscus (Pl. [98], fig. 1).

Shell three-sided pyramidal, thorny, about as long as broad, with three dentate edges. Framework very loose, with irregular polygonal meshes; in the middle of each of the three triangular sides a horizontal band of denser network. Basal plate with three very large simple collar-holes. The apical horn and the three feet are three-sided pyramidal, about half as long as the columella, with three prominent irregularly dentate edges. The horn is straight, whilst the three feet are hook-shaped, its distal end being curved downwards and inwards.

Dimensions.—Shell 0.11 long, 0.13 broad.

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

2. Euscenium archicyrtis, n. sp.

Shell three-sided pyramidal, smooth, nearly as long as broad, with three straight edges connected by irregular loose framework with polygonal meshes. Basal plate with three very large simple collar-holes. The apical horn and the three feet are three-sided prismatic, smooth, about twice as long as the columella, straight and widely divergent.

Dimensions.—Shell 0.08 long, 0.1 broad.

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

3. Euscenium hemisphæricum, n. sp.

Shell hemispherical smooth, half as long as broad, with small and numerous subregular circular pores. Basal plate with three large triangular simple collar-holes. Horn slender, three-sided prismatic, twice as long as the columella. Feet very slender, with three denticulate edges, widely divergent and curved like the quadrant of a circle.

Dimensions.—Shell 0.04 long, 0.06 broad.

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

4. Euscenium tricolpium, n. sp. (Pl. [53], fig. 12).

Archiscenium tricolpium, Haeckel, 1881, Prodromus et Atlas, loc. cit.

Shell cap-shaped, nearly hemispherical, with three vaulted hemispherical bosoms between the three arches ascending from the feet to the horn. Network very irregular, with polygonal meshes, of different form and size. Basal plate with three large primary and some smaller irregular accessory collar-holes. Horn slender, straight, twice as long as the columella. Feet of the same length, slender, widely divergent, slightly curved. The three edges of the horn and the feet are elegantly denticulated.

Dimensions.—Shell 0.04 long, 0.08 broad.

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

5. Euscenium tripospyris, n. sp. (Pl. [84], fig. 8).

Tripospyris euscenium, Haeckel, 1881, Prodromus et Atlas.

Shell nearly spherical, smooth, with numerous small circular pores. Basal plate also with numerous small pores. Horn and feet stout, three-sided prismatic, straight or slightly curved, about as long as the thin, somewhat curved columella. This species is closely allied to Tripospyris.

Dimensions.—Shell 0.11 to 0.12 diameter, horn and feet 0.08 to 0.1 long.

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

Subgenus 2. Euscenidium, Haeckel.

Definition.—Feet forked or branched.

6. Euscenium furcatum, n. sp.

Shell campanulate, smooth, with numerous irregular roundish pores. Basal plate with nine pores (three larger central and six smaller distal). Horn club-shaped, half as long as the columella. Feet twice as long, cylindrical, parallel, vertical, forked at the distal end. (Similar to Tripospyris semantis, Pl. [84], fig. 2, but without sagittal feet.)

Dimensions.—Shell 0.07 long, 0.06 broad; horn 0.04 long, feet 0.1 long.

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

7. Euscenium quadratum, n. sp.

Shell campanulate, smooth with subregular square pores. Basal plate with three large pores. Horn and feet of the same size and shape, twice as long as the columella, three-sided prismatic, each with four or five verticils of lateral branches. (Similar to the cephalis of Clathrocorys murrayi, Pl. [64], fig. 8, but with four free spines without connecting lattice-wings.)

Dimensions.—Shell 0.06 long, 0.05 broad; horn and feet 0.12 long.

Habitat.—Central Pacific, Station 272, surface.

8. Euscenium ramosum, n. sp.

Shell subspherical, rough, with small subregular circular pores. Basal plate with nine pores (three larger central and six smaller distal pores). Horn and feet of the same size and form, three to four times as long as the columella, three-sided prismatic, irregularly branched.

Dimensions.—Shell 0.06 diameter, horn and feet 0.15 to 0.2 long.

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

Genus 505. Cladoscenium,[[122]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) with a free branched internal columella, prolonged into an apical horn. Three basal feet free, without lateral wings.

The genus Cladoscenium differs from the preceding Euscenium only in the ramification of the internal columella, which bears one or more verticils of three ascending lateral branches. The three branches of each verticil lie in the same equidistant meridian planes as the three basal feet, and are inserted with their distal ends on the inner surface of the simple lattice-shell. The three feet are also branched, but without vertical lattice-wings. Cladoscenium is perhaps closely allied to Clathrocorys.

1. Cladoscenium fulcratum, n. sp.

Shell subspherical, smooth, with large irregular roundish pores. Basal plate with three large pores. Columella with a single verticil of three ascending lateral branches. Apical horn as long as the columella, simple, three-sided prismatic. Feet twice as long, widely divergent, straight, prismatic, with some irregular basal branches.

Dimensions.—Shell 0.06 diameter, horn 0.05 long, feet 0.1 long.

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

2. Cladoscenium ancoratum, n. sp. (Pl. [53], fig. 13).

Shell campanulate, smooth, with irregular polygonal pores. Basal plate with six pores (two large cardinal, two smaller jugular and two still smaller cervical pores). Columella with a single verticil of three ascending lateral branches (by mistake not distinct in the figure). Apical horn and the three feet of the same form and size, slender, prismatic, twice to three times as long as the shell, straight, in the distal half with three slender recurved branches, anchor-shaped.

Dimensions.—Shell 0.05 long, 0.04 broad; horn and feet 0.1 to 0.15 long.

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

3. Cladoscenium gladiatum, n. sp.

Shell subspherical, with irregular polygonal pores. Basal plate with three large pores. Columella with two verticils of three ascending lateral branches. Apical horn as long as the columella, three-sided prismatic. Feet of the same form, twice as long, in the distal half with two opposite transverse branches, sword-shaped.

Dimensions.—Shell 0.05 long, 0.06 broad; horn 0.04 long, feet 0.1 long.

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

4. Cladoscenium pinnatum, n. sp.

Shell campanulate, with irregular polygonal pores. Basal plate with four pores (two major cardinal and two minor jugular). Columella with two verticils of three ascending lateral branches, and prolonged into a slender prismatic apical horn of twice the length, which bears four such verticils. Feet twice as long as the horn, pinnate, each with four or five pairs of opposite lateral branches, decreasing towards the thin distal end.

Dimensions.—Shell 0.06 long, 0.05 broad; horn 0.1 long, feet 0.2 long.

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

5. Cladoscenium verticillatum, n. sp.

Shell campanulate, with subregular square pores. Basal plate with nine pores (three larger central and six smaller distal). Columella with three verticils of three ascending lateral branches. Apical horn and the three basal feet of equal size and similar form, four to six times as long as the columella, three-sided prismatic, each with four to five verticils of three lateral branches, which are irregularly ramified and tapering towards the distal end. (Similar to Clathrocorys teuscheri, Pl. [64], fig. 10, but with four free spines, without connecting lattice-wings.)

Dimensions.—Shell 0.07 long, 0.06 broad; horn and feet 0.2 to 0.25 long.

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

6. Cladoscenium pectinatum, n. sp. (Pl. [98], fig. 2).

Shell subspherical, with irregular roundish pores. Basal plate with three large holes. Columella with two verticils of three ascending lateral branches. Apical horn and the three feet of nearly the same size and form, three to four times as long as the columella, straight, three-sided prismatic, each with five to eight verticils of three simple lateral branches, tapering towards the distal end.

Dimensions.—Shell 0.07 long, 0.08 broad; horn and feet 0.16 to 0.22 long.

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

Genus 506. Archiscenium,[[123]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) with a free simple internal columella, prolonged into an apical horn. Three basal feet connected with the horn by three vertical lateral wings.

The genus Archiscenium and the following nearly allied Pteroscenium are derived from the two preceding genera, from which they differ in the development of three free vertical lateral lattice-wings; these arise from the upper edge of the three basal feet and connect them with the three edges of the apical horn. The basal part of the latter, enclosed in the shell, forms an internal free columella, which in Archiscenium is simple, not branched.

1. Archiscenium quadrispinum, n. sp. (Pl. [53], fig. 11).

Shell hemispherical, smooth, with a small number of large irregular polygonal meshes and thin bars. Basal lattice with three very large central meshes and six smaller peripheral meshes (two on the base of each foot). Apical horn and the three feet of equal size and similar form, slender, pyramidal, widely divergent, straight, as long as the shell-diameter. Three lateral wings small, little prominent, each with two or three irregular meshes. Central capsule subspherical.

Dimensions.—Shell 0.05 long, 0.1 broad.

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

2. Archiscenium clathrocorys, n. sp.

Shell campanulate, smooth, with numerous irregular square meshes. Basal lattice with three very large meshes. Apical horn and the three feet of equal size and similar form, three-sided prismatic, widely divergent, straight, twice as long as the shell-diameter. Three lateral wings broad, each with a basal row of few very large irregular roundish meshes, and several distal rows of small square meshes. This species is very similar to Clathrocorys murrayi (Pl. [64], fig. 8), but has no trace of thorax-wall. The latter species may be derived from the former by development of the thoracic lattice, which connects the three free feet.

Dimensions.—Shell 0.05 long, 0.06 broad.

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

3. Archiscenium tripterygium, n. sp.

Shell hemispherical, smooth, with numerous irregular roundish meshes of very different sizes. Basal lattice with four large meshes, two major cardinal and two minor cardinal pores. Apical horn and the three feet of similar form and size, slender prismatic, three to four times as long as the shell; the horn straight, the feet curved. Three lateral wings very delicate, with a basal row of few large irregular polygonal meshes, and several distal rows of similar small pores.

Dimensions.—Shell 0.04 long, 0.05 broad.

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

4. Archiscenium cyclopterum, n. sp. (Pl. [98], fig. 3).

Shell hemispherical, with small irregular roundish pores. Basal lattice with four large meshes, two major cardinal and two minor jugular pores. Apical horn and the three feet of similar form and size, slender prismatic, straight, twice to four times as long as the shell. Three lateral wings nearly semicircular, densely latticed, with the same pores as the shell, and smooth convex margin.

Dimensions.—Shell 0.05 long, 0.06 broad.

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

5. Archiscenium callimitra, n. sp.

Shell campanulate, with irregular polygonal pores. Basal lattice with nine meshes (three larger central and six smaller distal pores, as in Callimitra carolotæ, Pl. [63], fig. 8). Apical horn straight, prismatic, slender, conical, twice as long as the shell. Feet longer and more slender, slightly curved. Three lateral wings very broad, densely fenestrated, with irregular polygonal pores of the same shape as in the similar Callimitra carolotæ (Pl. [63], fig. 1).

Dimensions.—Shell 0.05 long, 0.04 broad.

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

Genus 507. Pteroscenium,[[124]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) with a free branched internal columella, prolonged into an apical horn. Three basal feet connected with the horn by three vertical lateral wings.

The genus Pteroscenium differs from the preceding Archiscenium only in the ramification of the internal columella, and therefore exhibits to it the same relation that Cladoscenium bears to Euscenium. The branches of the columella form also here verticils of ascending branches, three in each verticil, and their distal ends are inserted on the inner surface of the lattice-shell.

1. Pteroscenium arcuatum, n. sp. (Pl. [98], fig. 4).

Shell campanulate, smooth, nearly conical, somewhat broader than long, with irregular dense network of small circular pores. Columella straight, with two or three triradiate verticils of horizontal lateral branches, which are inserted in the shell-wall. Horn slender pyramidal, as long as the shell. Three divergent feet twice as long as the horn, strongly curved, thorny, three-edged; the distance of their pointed ends twice as broad as the shell. From the outer edge of each foot arise numerous ascending bristles, which are connected together and with similar lateral branches of the horn by curved arches, forming three delicate spiny vertical wings.

Dimensions.—Shell 0.06 long, 0.08 broad.

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

2. Pteroscenium arcadophorum, n. sp.

Shell campanulate, smooth, with irregular polygonal pores, very similar to the preceding species but with much broader wings, forming several arcades with three to five rows of irregular meshes. Columella with five or six triradiate verticils of lateral branches. Horn twice as long as the shell, of the same length as the strongly curved spinulate feet.

Dimensions.—Shell 0.09 long, 0.11 broad.

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

3. Pteroscenium pinnatum, n. sp. (Pl. [53], figs. 14, 15, 16).

Shell campanulate, smooth, somewhat longer than broad, with irregular delicate network of small roundish pores. Columella straight, with numerous (eight to twelve) triradiate verticils of ascending lateral branches, which are inserted in the shell-wall. The uppermost end of the columella is a conical apical horn. The three divergent feet are smooth, slender, conical, slightly curved, about as long as the shell, pinnate, with six to ten pairs of ascending lateral branches, parallel to those of the columella and inserted on the three vaulted lateral wings. (Fig. 14 exhibits the outside of the shell, fig. 15 the internal structure of the cortina, fig. 16 the basal view.)

Dimensions.—Shell 0.1 long, 0.12 broad.

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

4. Pteroscenium spinulosum, n. sp.

Shell campanulate, spinulate, about as long as broad, with small and numerous irregular polygonal pores, very similar to the preceding species, but differing in the more slender form of the horn and the feet, bearing more numerous lateral branches (twelve to sixteen pairs on each foot). Columella with six to eight triradiate verticils. Horn about as long as the shell.

Dimensions.—Shell 0.1 long, 0.1 broad.

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

5. Pteroscenium macropodium, n. sp.

Shell campanulate, spinulate, with irregular polygonal pores; very similar to the two preceding species, but differing in the size and shape of the three feet, which are for the most part solid, triangular, nearly parallel, vertical, very slender, three times as long as the shell, latticed only at the curved base, with few pairs of lateral branches. Columella with four to six triradiate verticils, as long as the stout triangular pyramidal horn.

Dimensions.—Shell 0.1 long, 0.08 broad.

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

6. Pteroscenium tripocolpum, n. sp.

Shell campanulate, spinulate, similar to Euscenium tricolpium (Pl. [53], fig. 12) with three vaulted hemispherical bosoms between the three delicate arachnoidal vertical wings. Network loose, very irregular, with polygonal meshes of very different sizes. Columella with three or four triradiate verticils, as long as the slender pyramidal horn. Three feet twice as long, somewhat curved, widely divergent, with three or four pairs of lateral branches. The three edges of the feet and of the horn are elegantly denticulated.

Dimensions.—Shell 0.06 long, 0.09 broad.

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

Genus 508. Peridium,[[125]] Haeckel, 1881, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) without internal columella, with an apical horn.

The genus Peridium (or Archiperidium, Prodromus, loc. cit.) and the two following nearly allied genera form together the small group of Archibursida, differing from the four preceding genera (the Euscenida) in the absence of an internal free columella. The three basal feet have therefore no direct connection with the apical horn. Peridium, the ancestral form of the Archibursida, may have originated either from Euscenium by reduction and loss of the columella, or directly from Tripospyris by loss of the sagittal ring and the longitudinal constriction.

Subgenus 1. Peridarium, Haeckel.

Definition.—Feet smooth, simple, neither spiny nor branched.

1. Peridium lasanum, n. sp.

Shell subspherical, smooth, with subregular circular pores. Basal plate with three large meshes. Horn apical, vertical, of the same size and form as the three divergent smooth feet, slender pyramidal, twice to three times as long as the shell.

Dimensions.—Shell-diameter 0.06 to 0.07, length of the three spines 0.15 to 0.2.

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

2. Peridium papillatum, n. sp.

Shell subspherical, papillate, with subregular circular pores. Basal plate with four meshes (two major cardinal and two minor jugular pores). Horn occipital, oblique, three-sided pyramidal, half as long as the shell and as the three widely divergent, subhorizontal, smooth feet.

Dimensions.—Shell diameter 0.07 to 0.08, length of the horn 0.04, of the feet 0.08.

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

3. Peridium curvipes, n. sp.

Shell hemispherical, thorny, with irregular roundish pores. Basal plate with six pores (two larger middle cardinal, two smaller anterior jugular and two smaller posterior cervical pores, as in Pl. [53], figs. 13, 18). Horn conical, oblique, arising from the middle of the occipital face, half as long as the shell. Feet slender, conical, curved, smooth, twice as long as the shell.

Dimensions.—Shell 0.04 long, 0.06 broad; horn 0.02 long; feet 0.08 long.

Habitat.—Tropical Pacific, Station 206, depth 2100 fathoms.

Subgenus 2. Archiperidium, Haeckel.

Definition.—Feet spiny or branched.

4. Peridium spinipes, n. sp. (Pl. [53], fig. 9).

Shell ovate, rough or thorny, with irregular roundish pores. Basal plate with four pores (two larger cardinal and two smaller jugular pores). Horn oblique, occipital, three-sided pyramidal, half as long as the shell, connected with the caudal foot by a prominent crest. Three feet horizontally expanded, prismatic, spiny, about as long as the shell.

Dimensions.—Shell 0.08 long, 0.06 broad; horn 0.04 long, feet 0.06 to 0.09 long.

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

5. Peridium palmipes, n. sp. (Pl. [53], fig. 10).

Shell ovate, smooth, with irregular roundish pores. Basal plate with three large pores. Horn oblique, three-sided pyramidal, about as long as the shell, inserted near its occipital base. Three feet prismatic, slender, half as long, ending with a broad dentate plate.

Dimensions.—Shell 0.06 long, 0.05 broad; horn 0.05 long, feet 0.03 long.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

6. Peridium alatum, n. sp. (Pl. [97], fig. 7).

Shell subspherical smooth, with regular circular, hexagonally-framed pores. Basal plate with nine pores (three larger central and six smaller distal pores). Horn apical, of equal size and the same form as the three feet, three-sided prismatic, with three broad prominent wings, somewhat longer than the shell.

Dimensions.—Shell 0.07 long, 0.08 broad; horn and feet 0.1 to 0.12 long.

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

7. Peridium cervinum, n. sp.

Shell subspherical, spiny, with subregular circular pores. Basal plate with four pores (?). Horn apical, conical, about as long as the shell. Feet three to four times as long, cylindrical curved, with irregular simple or forked branches like the antlers of a deer.

Dimensions.—Shell diameter 0.1, horn 0.1 long, feet 0.3 to 0.4 long.

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

Genus 509. Archipera,[[126]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) without internal columella, with two or more apical horns.

The genus Archipera differs from the preceding Peridium only in the multiplication of the apical horn, which in the latter is always simple. The number of horns is usually two or three, sometimes four or more. The species bearing three horns may be derived directly from Triceraspyris by loss of the sagittal ring.

1. Archipera cortiniscus, n. sp. (Pl. [98], fig. 5).

Shell ovate, thorny, with large roundish pores, which are closed by sieve-plates with numerous small porules. Basal plate with two pairs of simple large pores (two smaller jugular and two larger cardinal, similar to Pl. [98], fig. 10b). Two horns divergent, curved, slender, pyramidal; the apical horn longer than the shell, the frontal horn shorter. Three feet divergent, longer than the shell, three-sided prismatic, at the distal end club-shaped, thorny.

Dimensions.—Shell 0.1 long, 0.08 broad; horns and feet 0.11 to 0.14 long.

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

2. Archipera pentacantha, n. sp.

Shell pear-shaped, smooth, with numerous and small irregular roundish pores. Basal plate with three larger pores. Two horns and three feet of nearly equal size and similar form, three-sided prismatic, about as long as the shell diameter, somewhat curved. The apical horn stands on the apex, the frontal horn half-way up the shell.

Dimensions.—Shell 0.08 long, 0.06 broad; horns and feet 0.05 to 0.07 long.

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

3. Archipera bicornis, n. sp.

Shell ovate, rough, with small regular circular, sparsely scattered pores. Basal plate with four larger central and a peripheral coronal of twelve smaller pores. Two horns near the apex widely divergent, somewhat shorter than the shell, of equal size and similar form. Three feet twice as long, horizontally expanded. All five spines slender, three-sided pyramidal, straight.

Dimensions.—Shell 0.07 long, 0.06 broad; horns 0.05 long, feet 0.1 long.

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

4. Archipera tricornis, n. sp.

Shell subspherical, smooth, with subregular circular pores. Basal plate with four large meshes (two major cardinal and two minor jugular pores). On the apex three divergent pyramidal horns of different size, one larger occipital and two smaller frontal horns. Three feet prismatic, about twice as long as the shell.

Dimensions.—Shell diameter 0.05, length of the feet 0.1.

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

5. Archipera quadricornis, n. sp.

Shell ovate, smooth, with a small number of irregular roundish, widely scattered pores. Basal plate with four crossed meshes of nearly equal size. On the equator there arise four divergent prismatic horns of nearly equal size, three of which correspond to the three feet, whilst the fourth is opposite to the caudal foot. The three feet are also prismatic, as long as the shell, horizontally expanded. (Similar to the upper half of Lithomelissa decacantha, Pl. [56], fig. 2, but without thorax.)

Dimensions.—Shell 0.05 long, 0.04 broad; horns and feet 0.06 long.

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

6. Archipera multicornis, n. sp.

Shell hemispherical, spiny, with irregular polygonal pores. Basal plate with six meshes (?). Between the smaller spines of the surface arise six larger conical divergent horns. Three feet also conical, divergent, about twice as long as the shell and the horns.

Dimensions.—Shell 0.05 long, 0.07 broad; horns 0.05 long, feet 0.1 long.

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

Genus 510. Archibursa,[[127]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiperida (vel Monocyrtida triradiata clausa) without internal columella and without apical horn.

The genus Archibursa has probably arisen from Peridium by loss of the apical horn, and is the only genus of Archiperida which bears no horn. The three basal feet are well-developed. It differs from the similar Tristylospyris by the absence of the sagittal ring and the corresponding longitudinal constriction.

1. Archibursa tripodiscus, n. sp. (Pl. [98], fig. 6).

Shell subspherical, smooth, with irregular roundish pores. Basal plate with three large triangular pores of equal size (fig. 6). Three feet widely divergent, straight, three-sided prismatic, about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.07, length of the feet 0.09.

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

Family LX. Phænocalpida, n. fam.

Archiphormida et Archiphænida, Haeckel, 1881, Prodromus, pp. 428, 429.

Definition.—Monocyrtida multiradiata. (Cyrtoidea with a simple, not jointed shell, resembling a simple cephalis, with numerous radial apophyses (four to nine or more).

The family Phænocalpida, composed of the Archiphormida and Archiphænida of my Prodromus, comprises those Cyrtoidea in which the lattice-shell is quite without transverse constriction, but bears numerous radial apophyses. The two subfamilies differ in the shape of the basal mouth, which in the Archiphormida is a simple wide opening, but is closed in the Archiphænida by a lattice-plate.

Several Phænocalpida were formerly described by Ehrenberg, viz., Halicalyptra virginica (in 1844) and Litharachnium arachnodiscus (in 1872, called by him Carpocanium, though it is quite different from this genus, and closely allied to my Litharachnium tentorium, figured in 1862). These forms belong to the Archiphormida (with open mouth). Several fossil Archiphænida (with closed mouth) were figured by Ehrenberg, in 1875, as belonging to Petalospyris (ocellata, carinata, flabellum), though the absence of the sagittal ring and the corresponding longitudinal constriction demonstrates their character as Phænocalpis.

The Phænocalpida are probably an artificial family, composed of three or four (or perhaps more) different groups, which have a quite different origin. The Litharachnida (genera 511-515) and the Haliphormida (genera 516-518) are probably derived from the Sethophormida by loss of the cephalis, the retrograde metamorphosis of which may be observed in all its different stages. The Halicalyptrida (genera 519-521) are perhaps independent of the other Phænocalpida, and may be Archicorida which have produced a corona of teeth around the mouth, without relation to lost radial ribs. The Phænoscenida (Phænocalpis, Phænoscenium) may be derived from the Euscenida (genera 504-507) by interpolation of interradial feet between the three primary ones, or directly from the Plectoidea. The Calpophænida, on the other hand (Calpophæna, Archiphæna), may have arisen from the Zygospyrida (Petalospyris, Gorgospyris) by loss of the sagittal ring and the longitudinal constriction. The phylogeny of the Phænocalpida is therefore a very complicated problem, as yet unsolved.

Synopsis of the Genera of Phænocalpida.
I. Subfamily Archiphormida. Basal mouth of the shell a simple wide opening.Radial ribs enclosed in the wall of the shell, usually prolonged into free terminal feet.Shell slender, pyramidal (without horn).Shell simple, with simple network,511. Bathropyramis.
Shell simple, with double network,512. Cinclopyramis.
Shell double, with an outer mantle,513. Peripyramis.
Shell flatly campanulate or discoidal (without horn).Radial ribs simple,514. Litharachnium.
Radial ribs branched,515. Cladarachnium.
Shell ovate, urceolate or campanulate.Mouth smooth, constricted (no horn),516. Cystophormis.
Mouth, with a corona of feet.With horn,517. Haliphormis.
No horn,518. Archiphormis.
No radial ribs in the wall of the shell. Mouth surrounded by a corona of free terminal feet.Shell simple without mantle.With horn,519. Halicalyptra.
No horn,520. Carpocanistrum.
Shell double, with an external mantle (no horn),521. Arachnocalpis.
II. Subfamily Archiphænida. Basal mouth closed by a lattice-plate.In the axis of the shell-cavity a free columella.Columella simple,522. Phænocalpis.
Columella branched,523. Phænoscenium.
Shell-cavity simple, without axial columella.Apex with a horn,524. Calpophæna.
No apical horn,525. Archiphæna.
I. Subfamily Archiphormida. Basal mouth of the shell a simple wide opening.
Radial ribs enclosed in the wall of the shell, usually prolonged into free terminal feet.
Shell slender, pyramidal (without horn).
Shell simple, with simple network,
511. Bathropyramis.
Shell simple, with double network,
512. Cinclopyramis.
Shell double, with an outer mantle,
513. Peripyramis.
Shell flatly campanulate or discoidal (without horn).
Radial ribs simple,
514. Litharachnium.
Radial ribs branched,
515. Cladarachnium.
Shell ovate, urceolate or campanulate.
Mouth smooth, constricted (no horn),
516. Cystophormis.
Mouth, with a corona of feet.
With horn,
517. Haliphormis.
No horn,
518. Archiphormis.
No radial ribs in the wall of the shell. Mouth surrounded by a corona of free terminal feet.
Shell simple without mantle.
With horn,
519. Halicalyptra.
No horn,
520. Carpocanistrum.
Shell double, with an external mantle (no horn),
521. Arachnocalpis.
II. Subfamily Archiphænida. Basal mouth closed by a lattice-plate.
In the axis of the shell-cavity a free columella.
Columella simple,
522. Phænocalpis.
Columella branched,
523. Phænoscenium.
Shell-cavity simple, without axial columella.
Apex with a horn,
524. Calpophæna.
No apical horn,
525. Archiphæna.

Subfamily 1. Archiphormida, Haeckel, 1881, Prodromus, p. 428.

Definition.—Phænocalpida with the basal mouth of the shell open (vel Monocyrtida multiradiata aperta).

Genus 511. Bathropyramis,[[128]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with simple, slender pyramidal shell and numerous radial beams (six to nine or more). Network simple, with large, unfenestrated, quadrangular meshes.

The genus Bathropyramis and the following four nearly allied genera form together a peculiar group of Archiphormida, the Litharachnida, possessing near relations to Sethopyramis and the allied Sethophormida, from which they are probably derived by reduction and loss of the small cephalis. The shell in all these forms is distinctly pyramidal, composed of numerous divergent radial beams (commonly six to nine), which form the edges of the pyramid, and are connected by parallel horizontal rings. The quadrangular meshes so produced are quite simple in Bathropyramis. This genus cannot be sharply separated from Sethopyramis, its ancestral form.

Subgenus 1. Acropyramis, Haeckel, 1881, Prodromus, p. 428.

Definition.—Shell smooth, without spines on the surface.

1. Bathropyramis acephala, n. sp.

Shell smooth, slenderly pyramidal, with three cortinar pores at the apex and with six stout radial beams or longitudinal ribs, connected by twelve to sixteen complete hexagonal horizontal rings. Meshes nearly square, increasing gradually in size towards the mouth.

Dimensions.—Shell 0.25 long, 0.15 broad.

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

2. Bathropyramis quadrata, n. sp. (Pl. [54], fig. 1).

Shell smooth, slenderly pyramidal, with three cortinar pores at the apex and nine stout radial beams, connected by eight to twelve complete circular horizontal rings. Meshes subregular, square, increasing in size gradually towards the circular mouth.

Dimensions.—Shell 0.2 to 0.3 long, 0.12 to 0.2 broad.

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

3. Bathropyramis trapezoides, n. sp. (Pl. [54], fig. 3).

Shell smooth, broadly pyramidal, with four cortinar pores at the apex and eight (or sometimes nine) stout radial beams, connected by twelve to sixteen complete octagonal horizontal rings. Meshes trapezoidal, of nearly equal length, but gradually increasing in breadth.

Dimensions.—Shell 0.3 long, 0.3 broad.

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

4. Bathropyramis interrupta, n. sp. (Pl. [55], fig. 7).

Shell smooth, flatly pyramidal, nearly discoidal, with four cortinar pores at the apex and nine to ten stout radial beams, connected by eight to sixteen interrupted rings; the rings are complete only in the apical part, in the distal part more or less irregularly interrupted.

Dimensions.—Shell 0.12 long, 0.36 broad.

Habitat.—North Atlantic, Station 354, surface.

5. Bathropyramis medusa, n. sp.

Shell smooth, flatly pyramidal, nearly discoidal, with four cortinar pores and numerous radial beams (thirty to fifty); the four perradial of these are prolongations of the four cortinar beams, and alternate with four interradial of the same size. Between these are intercalated eight adradial beams arising from the third ring; and between the former and the latter, sixteen to twenty-four peripheral radial beams, arising from the fourth to the sixth ring. The inner four to six rings are complete, the outer ten to fifteen irregularly interrupted.

Dimensions.—Shell 0.08 long, 0.3 to 0.4 broad.

Habitat.—South Atlantic, Station 338, surface.

Subgenus 2. Cladopyramis, Haeckel, 1881, Prodromus, p. 428.

Definition.—Shell spiny, with prominent simple or branched spines on the surface.

6. Bathropyramis spinosa, n. sp.

Shell spiny, slenderly pyramidal, with three cortinar pores at the apex and with nine strong radial beams, connected by fifteen to twenty complete parallel rings. Meshes subregular square, increasing gradually in size. Surface covered with simple, strong conical spines, arising from the nodal points.

Dimensions.—Shell 0.24 long, 0.16 broad.

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

7. Bathropyramis ramosa, n. sp. (Pl. [54], fig. 4).

Shell spiny, slenderly pyramidal, with three cortinar pores at the apex, and with nine (or sometimes eight or ten) strong radial beams, connected by fifteen to eighteen complete parallel rings. Meshes subregular, square, increasing gradually in size. Surface covered with forked or irregularly branched spines, arising from the nodal points.

Dimensions.—Shell 0.3 long, 0.17 broad.

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

Genus 512. Cinclopyramis,[[129]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with simple, slender, pyramidal shell, and numerous radial beams (six to nine or more). Network double, with a delicate arachnoidal fenestration, filling up the large quadrangular meshes.

The genus Cinclopyramis differs from the preceding Bathropyramis in the development of a very delicate secondary network, filling up the large quadrangular meshes, which are produced by the crossing of the radial beams and the parallel horizontal rings. It therefore bears the same relation to the preceding genus that Plectopyramis does to Sethopyramis; it is perhaps derived directly from the former by loss of the small cephalis.

1. Cinclopyramis cribellum, n. sp.

Cinclopyramis cribellum = "Ladder of lattice-shape," Bury, 1862, Polycystins of Barbados, pl. xii. fig. 6.

Shell slender, pyramidal, with six strong radial ribs, which are connected by twelve to sixteen complete horizontal rings. Meshes trapezoidal, filled up by a very delicate and regular secondary network with square porules (two to four horizontal threads in each larger mesh).

Dimensions.—Shell 0.2 to 0.3 long, 0.12 to 0.16 broad.

Habitat.—Fossil in Barbados.

2. Cinclopyramis infundibulum, n. sp. (Pl. [54], fig. 7).

Shell slender, pyramidal, with nine strong radial ribs, which are connected by eighteen to twenty-four complete horizontal rings. Meshes subregular square, filled up by a very delicate and regular secondary network with square porules (ten to twelve horizontal threads in each larger mesh). Apex of the pyramid with three very small cortinar pores.

Dimensions.—Shell 0.3 to 0.4 long, 0.2 to 0.25 broad.

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

3. Cinclopyramis lithosestrum, n. sp.

Shell slender, pyramidal, with twelve strong radial ribs (six primary longer and six secondary shorter) connected by twelve to fifteen interrupted irregular rings. Meshes irregular square or trapezoidal, filled up by a delicate secondary network with irregular polygonal porules.

Dimensions.—Shell 0.4 to 0.5 long, 0.2 to 0.3 broad.

Habitat.—Fossil in Barbados.

Genus 513. Peripyramis,[[130]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with double, slenderly pyramidal shell, and numerous radial beams (six to nine or more). Network double, with an external arachnoidal or spongy envelope around the primary lattice-shell.

The genus Peripyramis differs from its probable ancestral form, Bathropyramis, by development of a delicate external envelope around the primary shell, and therefore bears to it the same relation that Spongopyramis among the Dicyrtida does to Sethopyramis. It may also be derived directly from the former by loss of the cephalis.

1. Peripyramis circumtexta, n. sp. (Pl. [54], fig. 5).

Shell slender, pyramidal, with nine strong radial beams, connected by fifteen to twenty transverse horizontal rings, which are partly complete, partly interrupted. Meshes subregular, square. From the nodal points of the surface there arise branched spines, which at equal distances from it are connected by thin threads, forming a delicate outer arachnoidal shell with large irregular polygonal meshes.

Dimensions.—Shell 0.32 long, 0.16 broad.

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

2. Peripyramis spongiosa, n. sp.

Shell slender, pyramidal, with nine strong radial beams, connected by twelve to eighteen irregular interrupted rings. Meshes irregular, square or polygonal. From the whole surface arise numerous branched spines, which by communication and dense ramification form an outer spongy envelope around the shell. (Similar to Spongopyramis spongiosa, Pl. [56], fig. 10.)

Dimensions.—Shell 0.45 long, 0.32 broad.

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

Genus 514. Litharachnium,[[131]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 835.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with flatly conical, tent-shaped or nearly discoidal shell, and numerous, simple, radial beams in its wall.

The genus Litharachnium, and the closely allied genus Cladarachnium, differ from the preceding similar genera mainly in the flat form of the depressed shell, which is not slenderly pyramidal, but more tent-shaped or nearly discoidal. The radial ribs are generally not straight, but more or less curved. The top of the tent exhibits three or four important meshes, the original pores of the cortinar septum. Litharachnium may be derived directly from Sethophormis by reduction and loss of the cephalis.

Subgenus 1. Litharachnidium, Haeckel.

Definition.—Apex with three cortinar pores (one odd sternal and two paired cardinal pores).

1. Litharachnium tentorium, Haeckel.

Litharachnium tentorium, Haeckel, 1862, Monogr. d. Radiol., p. 281, Taf. iv. figs. 7-10.

Shell flatly conical or tent-shaped, with concave lateral outlines. Apex with three equal cortinar pores. Twenty radial ribs at nearly equal distances. Between them very numerous and thin secondary ribs, crossed by more than one hundred concentric rings. Pores square, as in all the following species. Margin truncate, circular.

Dimensions.—Shell 0.35 long, 0.8 broad.

Habitat.—Mediterranean (Messina).

2. Litharachnium araneosum (Pl. [55], figs. 8, 10).

Shell flatly conical, nearly discoidal, with straight lateral outlines. Apex with three unequal cortinar pores (one odd smaller sternal and two paired larger cardinal pores). Twenty radial ribs at unequal distances, with numerous intercalated secondary ribs. Margin ciliate.

Dimensions.—Shell 0.18 long, 0.32 broad.

Habitat.—Central Pacific, Station 271, surface.

3. Litharachnium arachnodiscus, Haeckel.

Litharachnium arachnodiscus, Haeckel, 1862, Monogr. d. Radiol., p. 283.

Carpocanium arachnodiscus, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 296; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 8.

Shell flatly campanulate, nearly discoidal, with convex (?) lateral outlines. Apex with three unequal cortinal pores. Nine stronger radial primary ribs complete; between them numerous secondary intercalated ribs (sixty to seventy). Margin ciliate.

Dimensions.—Shell 0.03 long, 0.1 broad (?).

Habitat.—Arctic Ocean (between Greenland and Iceland), depth 1000 fathoms (Schaffner).

4. Litharachnium epeira, n. sp. (Pl. [55], fig. 9).

Shell flatly conical or tent-shaped, with concave lateral outlines. Apex with three unequal cortinar pores. Twelve stronger radial primary ribs complete; between them numerous (twenty-four to thirty-six) thinner secondary, and very numerous (more than one hundred) tertiary ribs. Margin reflexed, like the curved brim of a hat.

Dimensions.—Shell 0.12 long, 0.27 broad.

Habitat.—Central Pacific, Station 274, surface.

Subgenus 2. Litharachnoma, Haeckel.

Definition.—Apex with four cortinar pores (two anterior jugular and two posterior cardinal pores).

5. Litharachnium discoides, n. sp.

Shell flat, funnel-shaped, nearly discoidal, with concave outlines. Apex with four unequal cortinar pores (two smaller jugular and two larger cardinal pores). Twelve strong primary or perradial ribs alternating with twelve weaker secondary or interradial ribs; between these there are twenty-four shorter tertiary or adradial ribs, and in the outer flat, discoidal, half of the shell very numerous peripheral radial ribs (more than two hundred to three hundred). Margin flat, discoidal.

Dimensions.—Shell about 0.2 long, 1.12 broad.

Habitat.—Equatorial Atlantic, Station 347, surface.

6. Litharachnium pilidium, n. sp.

Shell flat, hat-shaped, with S-shaped outlines, in the upper half convex, in the lower half concave. Apex with four equal crossed cortinar pores. Thirty primary ribs of equal size; four of them are the prolongations of the four cortinar beams, eight intercalate between these secondary, and the other eighteen tertiary. Between them very numerous peripheral beams. Margin broad horizontal, reflexed like the brim of a "Bismarck" hat.

Dimensions.—Shell 0.17 long, 0.38 broad.

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

Genus 515. Cladarachnium,[[132]] Haeckel, 1881, Prodromus, p. 430.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with flatly conical, tent-shaped or nearly discoidal shell, and numerous branched radial beams.

The genus Cladarachnium differs from the preceding Litharachnium only in the ramification of the radial beams, the distal ends of which project over the margin of the shell. Only one species of the genus has been observed.

1. Cladarachnium ramosum, n. sp. (Pl. [55], figs. 5, 6).

Shell flatly conical or tent-shaped, with nearly straight lateral outlines; apical part somewhat higher. Apex with three cortinar pores surrounded by a few girdles of larger pores. From these there arise about twelve to fifteen strong radial beams at unequal distances; these are somewhat curved and irregularly branched. The network between them has irregular polygonal meshes and is more delicate towards the periphery. Margin with twenty-four to thirty irregular indentations or concave excisions, separated by the prominent distal ends of the branched ribs.

Dimensions.—Shell 0.16 long, 0.4 broad.

Habitat.—Central Pacific, Station 271, surface.

Genus 516. Cystophormis,[[133]] n. gen.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with ovate or urceolate shell and numerous radial ribs in its wall. Mouth more or less constricted, smooth, truncated. Apex without horn.

The genus Cystophormis, like the preceding genera, exhibits numerous prominent radial or longitudinal ribs in the wall of the urceolate shell; it differs from these in the constricted and truncated mouth, with smooth margin of the peristome.

1. Cystophormis pila, n. sp. (Pl. [52], fig. 1).

Shell balloon-shaped, subspherical, with twenty denticulate meridional ribs, alternating with twenty longitudinal rows of circular pores, which are twice as broad as the bars. Peristome constricted and then dilated, smooth, half as broad as the shell.

Dimensions.—Shell 0.11 long, 0.09 broad; mouth 0.06 broad.

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

2. Cystophormis ærostatica, n. sp. (Pl. [52], figs. 2, 3).

Shell balloon-shaped, subspherical, with twenty smooth meridional ribs, alternating with twenty longitudinal rows of circular pores, of the same breadth as the bars. Peristome constricted, about half as broad as the shell.

Dimensions.—Shell 0.09 long, 0.07 broad; mouth 0.03 broad.

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

3. Cystophormis spiralis, n. sp. (Pl. [51], fig. 9).

Shell ovate, one and a half times as long as broad, with twenty spirally convoluted, elegantly denticulated ribs, alternating with twenty spiral rows of small circular pores, of about the same breadth as the bars. Peristome constricted, very small, only one-seventh as broad as the shell.

Dimensions.—Shell 0.1 long, 0.07 broad; mouth 0.01 broad.

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

4. Cystophormis tabulata (Pl. [79], fig. 2).

Shell urceolate and tabulate, twice as long as broad with twenty-five to thirty denticulated longitudinal ribs crossed by twenty to twenty-four transverse rings. Pores therefore regularly disposed in longitudinal and transverse rows; each pore circular, with a square frame. Peristome constricted, scarcely half as broad as the shell.

Dimensions.—Shell 0.2 long, 0.1 broad; mouth 0.04 broad.

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

Genus 517. Haliphormis,[[134]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54 (sensu mutato).

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with numerous radial ribs in the wall of the campanulate shell, prolonged into free terminal feet. Apex with a horn.

The genus Haliphormis (with an apical horn) and the following Archiphormis (without a horn) comprise those Archiphormida in which the open mouth is more or less constricted and surrounded by a coronet of radial feet, as terminal prolongations of the radial ribs of its wall. The few forms, upon which Ehrenberg originally founded the genus Haliphormis, are partly not recognisable, partly belong to other genera. We therefore give here a new definition of the genus, as stated in my Prodromus, 1881, p. 428.

1. Haliphormis lagena, n. sp. (Pl. [97], fig. 5)

Shell bottle-shaped, twice as long as broad, tapering towards both ends, with nine longitudinal curved ribs. These are connected by irregular transverse beams, and the quadrangular meshes, so produced, are filled up by irregular, delicate, arachnoidal framework. The constricted mouth is half as broad as the middle part of the shell and surrounded by nine slender convergent feet, the free distal ends of the ribs. The apex bears a small knob with an oblique horn, perhaps the rudimentary cephalis of Sethamphora or Sethopyramis (?).

Dimensions.—Shell 0.6 to 0.7 long, 0.3 to 0.4 broad.

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

2. Haliphormis costata, n. sp.

Shell campanulate, somewhat longer than broad, with twelve prominent longitudinal ribs, alternating with twelve rows of regular circular pores. Mouth constricted half as broad as the shell, with twelve long triangular feet, formed by the free distal ends of the ribs. Apical horn short and stout, triangular pyramidal.

Dimensions.—Shell 0.12 long, 0.1 broad; mouth 0.07 long.

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

Genus 518. Archiphormis,[[135]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with numerous radial ribs in the wall of the campanulate or urceolate shell, prolonged into free terminal feet. Apex without horn.

The genus Archiphormis differs from the preceding Haliphormis, its probable ancestral form, in the absence of the apical horn. The number of the longitudinal ribs, which are prolonged into terminal feet, is from six to nine or twelve or even more.

1. Archiphormis cancellata, Haeckel.

(?) Halicalyptra cancellata, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 243.

Shell cup-shaped or campanulate, with six prominent ribs, prolonged into six terminal triangular feet, one-third as long as the shell. Ribs connected by five or six transverse horizontal rings; meshes between them rounded squarish. (As Ehrenberg has given no figure of this species, its identity with the Challenger specimen is doubtful.)

Dimensions.—Shell 0.08 long, 0.06 broad; mouth 0.04 broad.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

2. Archiphormis campanulata, n. sp.

Shell campanulate, with nine prominent denticulate ribs, prolonged into nine terminal feet, which are broad, lamellar, truncate, nearly vertical, one-third as long as the shell. Pores between the ribs circular, disposed in nine longitudinal and seven to eight transverse rows.

Dimensions.—Shell 0.09 long, 0.1 broad; mouth 0.06 broad.

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

3. Archiphormis urceolata, n. sp. (Pl. [98], fig. 11).

Shell urceolate, with nine smooth prominent curved ribs, prolonged into nine triangular convergent short feet, scarcely one-sixth as long as the shell. Pores between the ribs in nine regular longitudinal rows, twice or three times as broad as long, quadrangular, eight to twelve pores in each row. Mouth constricted, half as broad as the shell.

Dimensions.—Shell 0.13 long, 0.11 broad; mouth 0.06 broad.

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

Genus 519. Halicalyptra,[[136]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54 (sensu emendato).

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) without radial ribs in the wall of the campanulate or ovate shell. Mouth with a coronet of radial feet. Apex with a horn.

The genus Halicalyptra and the two following closely allied genera differ from the preceding Archiphormida in the absence of radial ribs. The multiradiate structure is indicated only by the terminal spines or feet, forming a coronet around the mouth. These feet are either the free ends of reduced ribs, or new productions of the peristome. Halicalyptra may be derived from Calpophæna and Petalospyris by loss of the basal lattice-plate of the cephalis. But it is also possible that it has been derived from Anthocyrtis by loss of the cephalis, and that its shell corresponds to the thorax of the latter.

Subgenus 1. Acrocalpis, Haeckel, 1881, Prodromus, p. 427.

Definition.—Shell smooth, without spines or thorns (other than the feet and the apical horn).

1. Halicalyptra virginica, Ehrenberg.

Halicalyptra virginica, Ehrenberg, 1854, Mikrogeol., Taf. xviii. fig. 110.

Halicalyptra virginica, Haeckel, 1862, Monogr. d. Radiol., p. 289.

Haliomma virginicum, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 71.

Acrocalpis virginica, Haeckel, 1881, Prodromus, p. 427.

Shell smooth, campanulate, nearly hemispherical. Pores subregular circular, about as broad as the bars. Horn conical, half as long as the shell. Peristome scarcely constricted, with six conical divergent feet, as long as the horn.

Dimensions.—Shell diameter 0.04 to 0.05, length of the feet 0.02.

Habitat.—Fossil in tertiary rocks of Barbados and North America (Richmond, Virginia).

2. Halicalyptra campanula, n. sp.

Podocyrtis spinosa, Bury, 1862, Polycystins of Barbados, pl. xvii. fig. 3.

Shell smooth, campanulate. Pores irregular, roundish, about as broad as the bars. Horn large conical, about as long as the shell. Peristome not constricted, with six large divergent feet, which are as long as the shell, lamellar, with dentate edges.

Dimensions.—Shell diameter 0.07, length of the feet 0.07.

Habitat.—Fossil in Barbados.

3. Halicalyptra ampulla, n. sp.

Petalospyris foveolata, var., Bury, 1862, Polycystins of Barbados, pl. ix. fig. 1.

Shell smooth, subspherical, inflate. Pores regular, circular, twice as broad as the bars. Horn slender conical, about as long as the shell. Peristome constricted, with six divergent cylindrical, irregularly curved feet, twice to three times as long as the shell.

Dimensions.—Shell diameter 0.12, feet 0.2 to 0.3 long.

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

4. Halicalyptra novena, n. sp.

Shell smooth, campanulate. Pores irregular, roundish. Horn slender conical, about as long as the shell. Peristome slightly constricted, with nine slender divergent feet of the same length. (Very similar to Petalospyris foveolata, Ehrenberg, but without internal columella and ring, with perfectly simple shell-cavity and open mouth.)

Dimensions.—Shell 0.09 diameter, feet 0.1 long.

Habitat.—Fossil in Barbados.

5. Halicalyptra petalospyris, n. sp. (Pl. [98], fig. 12).

Shell smooth, campanulate. Pores small, circular, irregularly scattered. Horn stout, pyramidal, about as long as the shell. Peristome scarcely constricted, with fifteen to twenty broad lamellar or lanceolate feet, which are twice to three times as long as the shell, parallel and vertical. (Very similar to Petalospyris flabellum, &c., Ehrenberg, 1875, loc. cit., Taf. xxii. figs. 6-8, but without any trace of sagittal ring or columella.)

Dimensions.—Shell 0.05 to 0.08 diameter, feet 0.15 to 0.25 long.

Habitat.—Central Pacific, Stations 266 to 268, depth 2700 to 2900 fathoms.

Subgenus 2. Echinocalpis, Haeckel, 1881, Prodromus, p. 427.

Definition.—Shell spiny, covered with numerous spines or thorns (besides the feet and the apical horn).

6. Halicalyptra spinosa, n. sp.

Shell spiny, ovate, inflate in the apical half. Pores irregular polygonal, four to eight times as broad as the bars. Peristome constricted, half as broad as the shell, with nine slender divergent feet, which like the apical horn are curved, twice to three times as long as the shell and five to ten times as long as the numerous bristles of the surface.

Dimensions.—Shell 0.08 long, 0.06 broad; feet 0.15 to 0.25 long.

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

7. Halicalyptra castanella, n. sp.

Shell spiny, nearly spherical. Pores irregular roundish. Peristome constricted, scarcely one-third as broad as the shell, with twelve to twenty slender, widely divergent feet, which like the horn are irregularly curved, and longer than the shell. (Very similar to certain forms of the Phæodarium Castanella, Pl. [113], fig. 2.)

Dimensions.—Shell 0.13 diameter, feet 0.15 to 0.18 long.

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

Genus 520. Carpocanistrum,[[137]] n. gen.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) without radial ribs in the wall of the campanulate or ovate shell. Mouth with a corona of radial feet. Apex without horn.

The genus Carpocanistrum differs from the similar preceding Halicalyptra in the loss of the apical horn. It is very nearly related to the Dicyrtid Carpocanium and may be easily confounded with it. But in the latter the uppermost part of the shell-cavity includes a rudimentary cephalis with a cortinar septum, whilst in Carpocanistrum the cephalis is entirely lost, and the inner cavity quite simple. The number of the feet of the peristome is from nine to twenty, sometimes more. The mouth is commonly more or less constricted.

1. Carpocanistrum novenum, n. sp.

Shell ovate, smooth, one and a third times as long as broad. Pores regular circular, hexagonally framed, three times as broad as the bars, eight to ten on the greatest breadth of the shell. Peristome strongly constricted, one-third as broad as the shell, with nine large ovate lamellar, slightly convergent feet.

Dimensions.—Shell 0.08 long, 0.06 broad; mouth 0.02 broad.

Habitat.—South Atlantic, Station 325, surface.

2. Carpocanistrum flosculum, n. sp. (Pl. [52], fig. 9).

Shell campanulate, rough, thick-walled, of equal breadth and length. Pores regular circular, of the same breadth as the bars, twelve to fifteen on the greatest breadth of the shell. Peristome slightly constricted, with twelve elegant lanceolate, nearly vertical, a little convergent feet.

Dimensions.—Shell 0.07 long, 0.07 broad; mouth 0.05 broad.

Habitat.—Equatorial Atlantic, Station 347, surface.

3. Carpocanistrum giganteum, n. sp.

Shell ovate, smooth, very thick-walled, one and a third times as long as broad. Pores very numerous and small, subregular circular, forty to fifty on the greatest breadth of the shell, of about the same breadth as the bars. Peristome small, constricted, scarcely one-fourth as broad as the shell, with twelve to fifteen short triangular vertical feet.

Dimensions.—Shell 0.28 to 0.31 long, 0.21 to 0.23 broad; mouth 0.06 to 0.07 broad.

Habitat.—Fossil in Barbados.

4. Carpocanistrum acephalum, n. sp. (Pl. [52], fig. 10).

Shell ovate, smooth, thin-walled, one and a fifth times as long as broad. Pores subregular circular, twice as broad as the bars, sixteen to twenty on the greatest breadth of the shell. Peristome slightly constricted, with fifteen to eighteen slender, slightly bent, nearly vertical, and parallel feet, which are half as long as the shell.

Dimensions.—Shell 0.12 long, 0.1 broad; mouth 0.07 broad.

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

5. Carpocanistrum evacuatum, n. sp. (Pl. [52], fig. 11).

Shell urceolate, smooth, thin-walled, one and a half times as long as broad. Pores regular circular, sixteen to twenty on the greatest breadth of the shell. Peristome slightly constricted, with twenty to twenty-five small triangular vertical feet.

Dimensions.—Shell 0.1 long, 0.07 broad; mouth 0.05 broad.

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

6. Carpocanistrum pyriforme, Haeckel.

Lithocarpium pyriforme, Stöhr, 1880, Palæontogr., vol. xxvi. p. 97, Taf. iii. fig. 10.

Shell pear-shaped or subspherical, one and a fourth times as long as broad. Pores roundish, polygonally framed (or with square meshes ?). Peristome strongly constricted, one-fourth as broad as the shell, somewhat tubular, with twelve to twenty short vertical and parallel feet. The position of this species is doubtful; perhaps it represents a peculiar genus.

Dimensions.—Shell 0.17 long, 0.14 broad; mouth 0.035 broad.

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

Genus 521. Arachnocalpis,[[138]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with an ellipsoidal or nearly spherical double shell; outer shell arachnoidal or spongy. Peristome small, constricted with a corona of numerous radial feet. No apical horn.

The genus Arachnocalpis differs from the other Archiphormida by possessing a double shell (like Peripyramis). The large shell, reaching nearly half a millimeter in length is either ellipsoidal or nearly spherical, and composed of an inner primary and an outer secondary shell. Its network is very delicate, in the outer envelope either spongy or arachnoidal. This very remarkable genus has probably no true relation to the other Archiphormida but has been derived from true Calpoidea (Mitrocalpis) by development of a corona around the mouth.

1. Arachnocalpis ellipsoides, n. sp. (Pl. [98], fig. 13).

Shell ellipsoidal, one and a half times as long as broad, on the apical pole hemispherical, on the basal pole coronate, with an elegant prominent funnel-shaped peristome, which is one-eighth as broad as the shell, fenestrated by very fine pores, and bears fifteen to twenty short conical divergent teeth. Inner shell with irregular polygonal meshes of very different size, separated by thin, finely-denticulate bars. Outer spongy shell very delicate, arachnoidal, with numerous prominent conical spongy papillæ. Central capsule ellipsoidal, half as long and broad as the shell.

Dimensions.—Shell 0.46 long, 0.32 broad; mouth 0.045 broad.

Habitat.—Central Pacific, Stations 271 to 274, surface.

2. Arachnocalpis sphæroides, n. sp.

Shell spheroidal, of the same structure as the preceding ellipsoidal species, with the same form of the spongy envelope; differing from it in the globose form and the shorter peristome, bearing only nine or ten small conical divergent teeth. Central capsule spherical.

Dimensions.—Shell 0.3 diameter, mouth 0.04 broad.

Habitat.—Central Pacific, Stations 265 to 270, surface.

Subfamily 2. Archiphænida, Haeckel, 1881, Prodromus, p. 429.

Definition.—Phænocalpida with the basal mouth of the shell fenestrated (vel Monocyrtida multiradiata clausa).

Genus 522. Phænocalpis,[[139]] n. gen.

Definition.—Archiperida (vel Monocyrtida multiradiata clausa) with an internal axial simple columella, prolonged outside into an apical horn.

The genus Phænocalpis and the following Phænoscenium comprise those Archiphænida in which the vertical axis of the shell-cavity is occupied by a simple or branched columella, arising from the centre of the base and prolonged into an apical horn. This columella may be either the vertical rod of a Plectaniscus or the remnant of an original ring of Petalospyris. The latter genus differs by its sagittal constriction.

1. Phænocalpis petalospyris, n. sp. (Pl. [97], fig. 4).

Shell subspherical, rough, with irregular, roundish pores, larger than the bars. Columella straight, central, thin, prolonged into a large apical horn with three dentate edges. Six basal feet curved, divergent, lamellar, with a middle rib and dentate edges.

Dimensions.—Shell 0.07 long, 0.05 broad; horn and feet 0.06 long.

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

2. Phænocalpis ocellata, Haeckel.

Petalospyris ocellata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xxii. fig. 9.

Shell subspherical, smooth, with irregular roundish pores, about as broad as the bars. Columella slightly curved and excentric, prolonged into a slender conical horn of the same length. Six basal feet similar to the horn, slightly divergent.

Dimensions.—Shell 0.06 long, 0.07 broad; horn and feet 0.05 long.

Habitat.—Fossil in Barbados.

3. Phænocalpis carinata, Haeckel.

Petalospyris carinata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xxii. fig. 6.

Shell campanulate, rough, with irregular roundish pores, smaller than the bars. Columella straight, central, prolonged into a stout conical horn of the same length. Nine basal feet slender, triangular, longer than the shell, nearly vertical, with a middle rib in the basal half.

Dimensions.—Shell 0.05 long, 0.06 broad; horn 0.04 long, feet 0.08 long.

Habitat.—Fossil in Barbados.

4. Phænocalpis flabellum, Haeckel.

Petalospyris flabellum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xxii. fig. 7.

Shell campanulate smooth, with very small circular pores, half as broad as the bars. Columella straight, central, prolonged into a pyramidal horn of half the length. Twelve to fifteen basal feet lamellar, linear, twice to three times as long as the shell, parallel and vertical, pointed at the distal end.

Dimensions.—Shell 0.04 long, 0.05 broad; horn 0.02 long, feet 0.1 to 0.12 long.

Habitat.—Fossil in Barbados.

Genus 523. Phænoscenium,[[140]] n. gen.

Definition.—Archiphænida (vel Monocyrtida multiradiata clausa) with an internal axial branched columella, prolonged outside into an apical horn.

The genus Phænoscenium differs from the preceding Phænocalpis in the branched columella, which is connected by three or six ascending branches with the inner wall of the shell. It bears therefore to the latter the same relation that Cladoscenium exhibits to Euscenium. The former genera may have been derived from the latter by interpolation of new interradial feet between the three primary perradial feet.

1. Phænoscenium hexapodium, n. sp. (Pl. [98], fig. 9).

Shell campanulate, smooth, about as long as broad. Network delicate, with irregular polygonal pores and thin bars. Columella with four to six ascending three-branched verticils, prolonged into the conical hollow apical horn (with six to eight smaller verticils) which is about as long as the shell. Six basal feet curved, divergent, of the same length, with pinnate middle rod.

Dimensions.—Shell 0.1 long, 0.11 broad; horn and feet 0.08 to 0.09 long.

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

2. Phænoscenium cladopodium, n. sp.

Shell campanulate, conical, smooth, somewhat broader than long. Network with irregular roundish pores, about as broad as the bars. Columella with a single verticil of three ascending branches. Horn pyramidal, stout, as long as the shell, with three dentate edges. Six feet divergent, slightly curved, very unequal; three primary (or perradial) very large, longer than the shell, three sided pyramidal, with three dentate edges; three secondary (or interradial) much smaller, simple, shorter than the shell.

Dimensions.—Shell 0.05 long, 0.06 broad; horn and feet 0.04 to 0.07 long.

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

3. Phænoscenium polypodium, n. sp.

Shell subspherical, about as long as broad, smooth. Network with regular circular pores, twice as broad as the bars. Columella with two verticils of three ascending branches, prolonged into a stout conical horn of twice the length. Twelve to fifteen conical curved divergent feet, about as long as the shell. The three primary feet are directly connected with the base of the columella.

Dimensions.—Shell 0.08 diameter, horn 0.15 long, feet 0.07 to 0.09 long.

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

Genus 524. Calpophæna,[[141]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiphænida (vel Monocyrtida multiradiata clausa) with an apical horn and simple internal cavity of the shell without axial columella.

The genus Calpophæna and the following closely tied Archiphæna differ from the two preceding genera of Archiphænida in the simple shell cavity, which encloses no columella. They may be derived either from the preceding Phænocalpis by loss of the columella, or directly from the Zygospyrida by reduction of the sagittal constriction and loss of the primary ring. Different subgenera may be distinguished in Calpophæna according either to the number of the feet or to their shape (being simple or branched).

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

Definition.—Feet simple, not branched nor forked.

1. Calpophæna tetrarrhabda, n. sp.

Shell subspherical, tuberculate, with subregular circular pores. Apical horn conical, about as long as the shell. Basal plate with a regular cross of four equal cortinar pores, separated by four bars; these are crossed in the sagittal and frontal diameter, and prolonged into four equal conical divergent feet, about as long as the shell.

Dimensions.—Shell 0.1 diameter, horn and feet 0.1 to 0.12 long.

Habitat.—South Pacific, Station 297, depth 1775 fathoms.

2. Calpophæna hexarrhabda, n. sp. (Pl. [53], figs. 17, 18).

Shell subspherical, rough, with irregular roundish pores. Apical horn conical, shorter than the shell. Basal plate (fig. 18) with three pairs of triangular pores, two larger (cardinal) pores in the middle, two smaller (cervical) at the dorsal, and two intermediate (jugular) at the ventral side. The bars between them are prolonged into six equal cylindrical divergent feet, nearly as long as the shell, provided with a spiny knob at the end.

Dimensions.—Shell 0.09 long, 0.08 broad; horn and feet 0.06 to 0.08 long.

Habitat.—Tropical Pacific, Station 224, depth 1850 fathoms.

3. Calpophæna ennearrhabda, n. sp.

Shell subspherical, spiny, with irregular, roundish pores. Apical horn cylindrical, longer than the shell. Basal plate with nine collar pores, three larger central alternating with three pairs of smaller peripheral (like Pl. [87], fig. 2). Corona with nine slender cylindrical, slightly curved, divergent feet, somewhat longer than the shell.

Dimensions.—Shell 0.11 long, 0.1 broad; horn and feet 0.12 to 0.15 long.

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

4. Calpophæna enneaphylla, n. sp.

Shell ovate, smooth, with regular circular pores. Apical horn pyramidal, half as long as the shell. (Basal plate with four cortinar pores?) Corona with nine broad, lamellar, truncate, vertical feet, about as long as the horn.

Dimensions.—Shell 0.12 long, 0.09 broad; horn and feet 0.06 long.

Habitat.—Central Pacific, Station 271, surface.

5. Calpophæna petalospyris, n. sp.

Shell campanulate, tuberculate, with irregular, roundish pores. Apical horn conical, shorter than the shell. (Basal plate with nine pores?) Corona with twelve to twenty broad, lamellar, truncate, vertical feet, of different sizes, somewhat irregular.

Dimensions.—Shell 0.08 long, 0.09 broad; horn and feet 0.07 to 0.12 long.

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

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

Definition.—Feet branched or forked.

6. Calpophæna tetracorethra, n. sp.

Shell subspherical, smooth, with irregular, roundish pores. Basal plate with four larger pores. Apical horn and the four divergent basal feet of equal size and similar form, three to four times as long as the shell, slender, bristle-shaped, curved, in the distal half irregularly branched. (Very similar to the remarkable Tetraspyris tetracorethra, Pl. [53], figs. 19, 20, but with shorter appendages and with simple spherical shell, which exhibits no trace of sagittal ring and constriction.)

Dimensions.—Shell 0.12 diameter, horn and feet 0.3 to 0.5 long.

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

7. Calpophæna hexacorethra, n. sp.

Shell subspherical, smooth, similar to the preceding species. Basal plate with six pores. Apical horn and the six divergent feet twice to three times as long as the shell, bristle-shaped, irregularly curved and branched. (Similar to Hexaspyris hexacorethra, Pl. [95], fig. 8, but without sagittal ring and constriction.)

Dimensions.—Shell 0.11 long, 0.13 broad; horn and feet 0.2 to 0.3 long.

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

Genus 525. Archiphæna,[[142]] Haeckel, 1881, Prodromus, p. 429.

Definition.—Archiphænida (vel Monocyrtida multiradiata clausa), with simple internal cavity of the shell, without apical horn and axial columella.

The genus Archiphæna has the same simple cavity of the shell as the preceding Calpophæna, but differs from it in the loss of the apical horn. It bears therefore to the latter the same relation that Gorgospyris does to Petalospyris. The two former genera may be derived from the two latter by loss of the sagittal ring and constriction.

Subgenus 1. Coronophæna, Haeckel, 1881, Prodromus, p. 429.

Definition.—Feet simple, not branched nor forked.

1. Archiphæna gorgospyris, n. sp. (Pl. [98], figs. 10, 10a).

Shell hemispherical, smooth, with small subregular, circular pores. Collar septum with four large pores (fig. 10a). Twelve to fifteen feet, divergent, lamellar, truncate, about as long as the shell. (Similar to certain forms of Gorgospyris, Pl. [87], figs. 1 to 3, but with simple shell cavity, without sagittal ring and constriction, and without a columella.)

Dimensions.—Shell 0.08 long, 0.04 broad; feet 0.03 to 0.04 long.

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

2. Archiphæna corona, n. sp.

Shell crown-shaped, somewhat broader than long, at the base flattened, papillate, with irregular roundish pores. Twenty to twenty-five feet, broad, lamellar, truncate, nearly vertical, about twice as long as the shell.

Dimensions.—Shell 0.1 long, 0.12 broad; feet 0.2 to 0.22 long.

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

Subgenus 2. Stephanophæna, Haeckel, 1881, Prodromus, p. 429.

Definition.—Feet branched or forked.

3. Archiphæna stephanoma, n. sp.

Shell campanulate, somewhat longer than broad, with subregular, circular pores. Margin of the flattened base with a corona of about twenty unequal feet, which are partly simple, partly irregularly branched, and about as long as the shell.

Dimensions.—Shell 0.11 long, 0.03 broad; feet 0.08 to 0.12 long.

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

Family LXI. Cyrtocalpida, n. fam.

Archicorida et Archicapsida, Haeckel, 1881, Prodromus, pp. 427, 428.

Definition.—Monocyrtida eradiata. (Cyrtoidea with a simple, not jointed shell, representing a simple cephalis without radial apophyses.)

The family Cyrtocalpida, composed of the Archicorida and Archicapsida of my Prodromus, comprises those Cyrtoidea in which the lattice-shell is quite simple, without transverse constriction, and without radial apophyses. The two subfamilies differ in the shape of the basal mouth, which in the Archicorida is a simple wide opening, but in the Archicapsida is closed by a lattice-plate.

Only a few species of this family were formerly known. Ehrenberg, in 1838, founded upon these the genus Cornutella, one of the three oldest genera of Polycystina (Cornutella, Lithocampe, Haliomma). In 1862 I described some living forms, with a central capsule, as Cyrtocalpis. The Challenger collection contains a large number of new genera and species.

Probably the family Cyrtocalpida is an artificial group, comprising two or more different subfamilies of very different origin. The Cornutellida (Cornutella, Cornutanna) have probably been derived from the Sethocorida by loss of the cephalis, so that their conical shell represents a thorax alone. The Mitrocalpida on the other hand (genera 528-531) may be originally simple ovate shells (like Gromia and Lecythium), arising independently from the Nassellida. The Archicapsida (Halicapsa, Archicapsa) are probably derived from the Zygospyrida (Dictyospyris, Circospyris) by loss of the sagittal ring and constriction. This is nearly certain, when the three or four typical cortinar pores appear in their basal plate. Some forms of Halicapsa may be easily confounded with some forms of Prunoidea (Lithapium).

Those Cyrtocalpida, which possess a central capsule with three or four lobes, are probably derived from Tripocyrtida by loss of the three feet, or from Sethocyrtida by loss of the cephalis, since the lobes indicate the original presence of cortinar pores and of a cephalis. Those Cyrtocalpida, however, in which a simple ovate shell encloses a simple central capsule without lobes, may be original "Monocyrtida eradiata," without relation to any radial ancestral forms.

Synopsis of the Genera of Cyrtocalpida.

I. Subfamily Archicorida.

Basal mouth of the shell a simple wide opening.

Shell with simple lattice-work (not double or spongy).Shell conical, gradually dilated towards the mouth.With horn,526. Cornutella.
No horn,527. Cornutanna.
Shell ovate or urceolate, with constricted mouth.With horn,528. Archicorys.
No horn,529. Cyrtocalpis
Shell not simply latticed.Shell ovate, double, with an external mantle,530. Mitrocalpis.
Shell ovate, with spongy irregular, lattice-work531. Spongocyrtis.

II. Subfamily Archicapsida.

Mouth closed by a lattice plate.

Shell with an apical horn,532. Halicapsa.
Shell without horn on the apex,533. Archicapsa.
I. Subfamily Archicorida. Basal mouth of the shell a simple wide opening.
Shell with simple lattice-work (not double or spongy).
Shell conical, gradually dilated towards the mouth.
With horn,
526. Cornutella.
No horn,
527. Cornutanna.
Shell ovate or urceolate, with constricted mouth.
With horn,
528. Archicorys.
No horn,
529. Cyrtocalpis
Shell not simply latticed.
Shell ovate, double, with an external mantle,
530. Mitrocalpis.
Shell ovate, with spongy irregular, lattice-work
531. Spongocyrtis.
II. Subfamily Archicapsida. Mouth closed by a lattice plate.
Shell with an apical horn,
532. Halicapsa.
Shell without horn on the apex,
533. Archicapsa.

Subfamily 1. Archicorida, Haeckel, 1881, Prodromus, p. 427.

Definition.—Cyrtocalpida, with the basal mouth of the shell open (vel Monocyrtida eradiata aperta).

Genus 526. Cornutella,[[143]] Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 128.

Definition.—Archicorida with conical shell, gradually dilated towards the wide open mouth. Apex armed with a horn.

The genus Cornutella is one of the three oldest genera of Polycystina, described by Ehrenberg, in 1838 (Cornutella, Lithocampe, and Haliomma). He afterwards enumerated, in 1872 and 1875, a large number of fossil and living species, the majority of which, however, belong to other genera of Monocyrtida and Dicyrtida (at least six or seven different genera). We retain here as the true type of the genus the oldest known species:—Cornutella clathrata, and the nearly allied forms Cornutella stylophæna, Cornutella mitra, Cornutella circularis, &c. The simple conical shell exhibits no distinct trace of an original cephalis, excepting the apical horn; it may have originated either independently, or been derived from Sethoconus, by loss of the cephalis.

Subgenus 1. Cornutellium, Haeckel.

Definition.—Axis of the conical shell straight. Pores polygonal, or roundish with polygonal frames.

1. Cornutella hexagona, n. sp. (Pl. [54], fig. 9).

Shell slender, conical, with straight outlines. Pores subregular, hexagonal, gradually increasing in size towards the mouth; in about ten to twelve longitudinal series, in the upper part very small. Horn slenderly conical, nearly bristle-shaped, long.

Dimensions.—Shell 0.1 to 0.15 long, 0.04 to 0.06 broad.

Habitat.—Central Pacific, Stations 265 to 274, surface, and at different depths.

2. Cornutella sethoconus, n. sp. (Pl. [54], fig. 10).

Shell slender, conical, with undulate outlines. Pores subregular, hexagonal, gradually increasing in size towards the mouth, in about fifteen to eighteen longitudinal series, in the upper part circular. Horn small, conical, short. The network is not so delicate as in the preceding similar species.

Dimensions.—Shell 0.12 to 0.16 long, 0.06 to 0.08 broad.

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

3. Cornutella distenta, Ehrenberg.

Cornutella distenta, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vi. III. fig. 3.

Shell slender, conical, with straight outlines. Pores small, circular, regularly disposed in six to eight alternating longitudinal rows, each pore surrounded by a large rhombic frame. The connected frames form together a regular rhombic framework with obliquely crossed crests. Horn conical, stout, large.

Dimensions.—Shell 0.1 to 0.15 long, 0.04 to 0.06 broad.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg.

4. Cornutella stiligera, Ehrenberg.

Cornutella stiligera, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 1; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 68, Taf. ii. fig. 3.

Shell slender, conical, with straight outlines. Pores subregular, rhombic or nearly square, disposed in oblique series, separated by parallel obliquely ascending rings, which are crossed by interrupted parallel bars. Horn slenderly conical or bristle-shaped, thin and long.

Dimensions.—Shell 0.08 to 0.12 long, 0.03 to 0.04 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Cornutissa, Haeckel, 1881, Prodromus, p. 427.

Definition.—Axis of the conical shell straight. Pores circular or roundish, without polygonal frames.

5. Cornutella circularis, Ehrenberg.

Cornutella circularis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 4.

Shell wide, conical or funnel-shaped, with straight outlines. Pores very large, circular, ten to twenty times as broad as the bars, in about nine to twelve longitudinal alternating rows, increasing gradually towards the mouth. Horn very large, cylindrical.

Dimensions.—Shell 0.1 to 0.15 long, 0.08 to 0.12 broad.

Habitat.—Fossil in Barbados.

6. Cornutella mitra, Ehrenberg.

Cornutella mitra, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 8.

Shell wide, conical, campanulate, with convex outlines. Pores subregular, circular, nearly equal in size, not regularly disposed in rows. Horn conical, stout.

Dimensions.—Shell 0.12 to 0.16 long, 0.08 to 0.12 broad.

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

7. Cornutella clathrata, Ehrenberg.

Cornutella clathrata, Ehrenberg, 1838, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 129; Mikrogeol., Taf. xxii. fig. 39.

Cornutella clathrata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. ii. fig. 9.

Shell wide, conical with slightly convex outlines. Pores regular, circular, gradually increasing in size towards the mouth, disposed in twelve to fifteen longitudinal alternating rows. Horn short and stout, conical. (Compare Cornutella curvata.)

Dimensions.—Shell 0.15 to 0.2 long, 0.06 to 0.09 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; also fossil in tertiary rocks of Barbados, Nikobar and Sicily.

8. Cornutella stylophæna, Ehrenberg.

Cornutella stylophæna, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vi. III. fig. 1.

? Cornutella tumens, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vi. III. fig. 4.

Shell slender, conical, with undulate outlines. Pores subregular, circular, gradually increasing in size, disposed in six to nine quincuncial alternating longitudinal rows. Horn very long, cylindro-conical, sometimes about as long as the shell.

Dimensions.—Shell 0.1 to 0.13 long, 0.04 to 0.06 broad.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms.

9. Cornutella granulata, Ehrenberg.

Cornutella granulata, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. vi. III. fig. 5.

Shell slender, conical, nearly cylindrical, with straight outlines, rounded at the apex. Pores very small and numerous, punctiform, disposed into very numerous parallel transverse rows. Horn small, conical (may be perhaps the shell of a Tintinnoid Infusorium?).

Dimensions.—Shell 0.08 long, 0.02 broad.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms.

10. Cornutella annulata, Ehrenberg.

Cornutella annulata, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ii. fig. 16.

Shell slender, conical, nearly cylindrical, with straight outlines, rounded at the apex. Pores small and numerous, regular circular, of equal size, regularly disposed in ten to fifteen parallel transverse series. Horn bristle-shaped. (Compare Artostrobus annulatus, Cornutella annulata, Bailey.)

Dimensions.—Shell 0.1 to 0.13 long, 0.03 to 0.04 broad.

Habitat.—Cosmopolitan, Atlantic, Pacific, surface.

Subgenus 3. Cornutosa, Haeckel, 1881, Prodromus, p. 427.

Definition.—Axis of the conical shell curved. Pores circular or roundish.

11. Cornutella curvata, Haeckel.

Cornutella clathrata, var., Ehrenberg, 1854, Mikrogeol., Taf. xxii. figs. 39a, b, c.

Cornutosa clathrata, Haeckel, 1881, Prodromus, p. 427.

Shell slender, conical, with curved axis; the curve lies in one plane and is not spirally convoluted. Pores subregular, circular, of nearly equal size, quincuncially disposed. Horn short, conical.

Dimensions.—Shell 0.1 to 0.15 long, 0.04 to 0.06 broad.

Habitat.—Fossil in tertiary rocks of Sicily (Caltanisetta).

12. Cornutella spiralis, n. sp.

Cornutura spiralis, Haeckel, 1881, Prodromus, p. 427.

Shell slender, conical, nearly cylindrical, very long, spirally contorted; its axis is an ascending spiral line with two or three windings, widely distant. Pores irregular, square, small and numerous.

Dimensions.—Shell 0.2 to 0.25 long, 0.05 to 0.08 broad.

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

Genus 527. Cornutanna,[[144]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archicorida with conical shell, gradually dilated towards the wide open mouth. Apex without horn.

The genus Cornutanna has the same simple conical shell as the preceding Cornutella, but differs from it in the total absence of an apical horn. It bears therefore to the latter the same relation that Cyrtocalpis does to Archicorys. It may be derived from Sethoconus by complete reduction of the cephalis and its horn.

1. Cornutanna orthoconus, n. sp.

Shell slender, conical, with straight axis and straight outlines. Pores subregular, circular, quincuncially disposed in nine to twelve alternating longitudinal series, gradually increasing in size towards the mouth.

Dimensions.—Shell 0.1 to 0.12 long, 0.03 to 0.04 broad.

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

2. Cornutanna cyrtoconus, n. sp.

Shell slender, conical, with curved axis; the curve lies in one plane as in the similar Cornutella curvata; the pores are smaller and more numerous than in this latter species, and the rounded apex bears no horn.

Dimensions.—Shell 0.12 to 0.16 long, 0.05 to 0.07 broad.

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

3. Cornutanna loxoconus, n. sp.

Shell wide, conical, with irregularly curved axis; the parts of the curve do not lie in one plane. Pores very small and numerous, of nearly equal size.

Dimensions.—Shell 0.2 long, 0.12 broad.

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

Genus 528. Archicorys,[[145]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archicorida with simple urceolate or ovate shell, constricted towards the mouth. Apex armed with a horn.

The genus Archicorys and the following closely allied Cyrtocalpis differ from the two preceding genera in the ovate or urceolate form of the shell, which is more or less constricted towards the terminal mouth. The upper pole in Archicorys bears an apical horn, which is absent in Cyrtocalpis. The origin of these two genera may be the same, probably arising directly from Nassellida, and independently of the triradiate Cyrtoidea or bilocular Spyroidea. (Compare p. [1179].)

1. Archicorys galea, n. sp.

Shell smooth urceolate. Pores large, in the middle part hexagonal, towards both ends smaller and polygonal. Apical horn stout, three-sided pyramidal, half as long as the shell. Mouth with a short tubular peristome, about one-third as broad as the shell.

Dimensions.—Shell (without horn) 0.15 long, 0.12 broad; horn 0.07 long, mouth 0.05 broad.

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

2. Archicorys ampulla, n. sp.

Shell smooth, thin-walled, bottle-shaped, in the upper half conical, in the lower half inflate, subspherical. Pores subregular, circular, of the same breadth as the bars. Horn conical, stout, /about one-third as long as the shell. Mouth truncate, without peristome, about half as broad as the shell.

Dimensions.—Shell 0.15 long, 0.1 broad; horn 0.05, mouth 0.05.

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

3. Archicorys microstoma, n. sp. (Pl. [51], fig. 12).

Shell rough, thick-walled, ovate. Pores large, subregular, circular, twice to four times as broad as the bars. Horn small, conical, not larger than one pore. Mouth very small, truncate, scarcely larger than one pore.

Dimensions.—Shell 0.1 long, 0.07 broad; horn 0.012, mouth 0.015.

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

4. Archicorys globosa, n. sp.

Shell nearly spherical, thorny, thick-walled. Pores very large, circular, separated by spinulate frames, smaller towards each pole. Horn conical, large, nearly as long as the radius of the shell; mouth truncate, simple, about one-third as broad as the shell.

Dimensions.—Shell diameter 0.13, horn 0.06, mouth 0.04.

Habitat.—Fossil in Barbados.

5. Archicorys ovata, n. sp. (Pl. [51], fig. 10).

Shell ovate, rough, thick-walled. Pores regular, circular, of equal size, very small and numerous, quincuncially disposed. Horn small, conical, sometimes (as in the figured specimen) rudimentary. When it becomes lost, the species may be called Cyrtocalpis ovata. Mouth truncate, small, simple, one-sixth as broad as the shell.

Dimensions.—Shell 0.2 long, 0.15 broad; horn 0.01 to 0.03 long, mouth 0.03 broad.

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

Genus 529. Cyrtocalpis,[[146]] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 835.

Definition.—Archicorida with simple urceolate or ovate shell, constricted towards the mouth. Apex without horn.

The genus Cyrtocalpis comprises a large number of common, very primitive Monocyrtida, which in the simple ovate or urceolate form of the shell resemble the well known Gromia among the Thalamophora. Its basal mouth is more or less constricted, as in the preceding genus Archicorys, from which it differs in the total absence of an apical horn. There is no trace of any triradial structure, excepting in some smaller species, in which the basal part of the central capsule is trilobate; these may be derived from the Dicyrtides Sethocorys or Dictyocephalus, by loss of the cephalis and the cortinar septum. But the larger species, which have a quite simple, ovate, central capsule (Pl. [51], fig. 13), have probably an independent origin, from Cystidium.

1. Cyrtocalpis urceolus, n. sp. (Pl. [51], fig. 13).

Shell smooth, urceolate, with very delicate and elegant network. Pores in the middle part large, regular, hexagonal, towards each pole smaller, irregular, roundish or polygonal. Mouth with broad, hyaline, annular peristome, about one-third as broad as the shell.

Dimensions.—Shell 0.16 long, 0.12 broad; mouth 0.05 broad.

Habitat.—Mediterranean (Portofino near Genoa), surface.

2. Cyrtocalpis reticulum, n. sp.

Shell smooth, urceolate, very similar to the preceding species, but differing from it in the densely reticulated framework of the shell, which is composed of very numerous and small, irregular, polygonal meshes of nearly equal size. Mouth without peristome, half as broad as the shell.

Dimensions.—Shell 0.18 long, 0.15 broad; mouth 0.07 broad.

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

3. Cyrtocalpis amphora, Haeckel.

Cyrtocalpis amphora, Haeckel, 1862, Monogr. d. Radiol., p. 286, Taf. v. fig. 2.

Shell smooth, urceolate with regular, circular pores of equal size, of about the same breadth as the bars. Mouth with smooth peristome, about half as broad as the shell.

Dimensions.—Shell 0.12 long, 0.08 broad; mouth 0.04 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific; surface, and at various depths.

4. Cyrtocalpis urna, Stöhr.

Cyrtocalpis urna, Stöhr, 1880, Palæontogr., vol. xxvi. p. 96, Taf. iii. fig. 7.

Shell smooth, urceolate, with subregular, circular pores of different sizes, gradually increasing towards the mouth, of about the same breadth as the bars. Mouth without peristome (?), about half as broad as the shell.

Dimensions.—Shell 0.09 long, 0.06 broad; mouth 0.035 broad.

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

5. Cyrtocalpis sethopora, n. sp. (Pl. [52], fig. 4).

Shell smooth, urceolate, very thin-walled, with large irregular roundish meshes, each of which is closed by a thin porous sieve-plate. Mouth two-thirds as broad as the shell, with a broad, emarginate, longitudinally striped peristome. (Perhaps the shell of a Tintinnoid Infusorium?)

Dimensions.—Shell 0.08 long, 0.05 broad; mouth 0.03 broad.

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

6. Cyrtocalpis compacta, n. sp. (Pl. [52], figs. 7, 8).

Shell smooth, ovate, very thick-walled, with small, subregular, circular pores of equal size, perpendicularly perforating the wall, about half as broad as the bars. Mouth small, only one-third as broad as the compact shell. (Perhaps a reduced Lithocampe or Lithomitra?)

Dimensions.—Shell 0.08 long, 0.04 broad; mouth 0.015 broad.

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

7. Cyrtocalpis lithomitra, n. sp. (Pl. [52], figs. 5, 6).

Shell smooth, slender, ovate, nearly cylindrical, with small subregular, circular pores, which are disposed in nine to twelve transverse rows, and obliquely ascending perforate the wall. Mouth wide, without peristome, about two-thirds as broad as the shell. (Compare Lithomitra, Pl. [79].)

Dimensions.—Shell 0.09 long, 0.045 broad; mouth 0.03 broad.

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

8. Cyrtocalpis ovulum, n. sp.

Cyrtocalpis obliqua, var. ovulum, Haeckel, 1862, Monogr. d. Radiol., p. 286, Taf. v. fig. 3.

Shell smooth, broad, ovate, with very numerous and small regular circular pores, quincuncially disposed, twice as broad as the bars. Mouth without peristome, about half as broad as the shell.

Dimensions.—Shell 0.09 long, 0.047 broad; mouth 0.04 broad.

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

9. Cyrtocalpis obliqua, Haeckel.

Cyrtocalpis obliqua, Haeckel, 1862, Monogr. d. Radiol., p. 286, Taf. v. figs. 4-11.

Shell smooth, irregularly ovate, more or less oblique, variable in size and form, sometimes nearly spherical, at other times subcylindrical. Pores subregular, circular, once or twice the breadth of the bars. Mouth simple without peristome, about half as broad as the shell.

Dimensions.—Shell 0.07 to 0.1 long, 0.05 to 0.08 broad; mouth 0.03 to 0.04 broad.

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

10. Cyrtocalpis gromia, n. sp. (Pl. [51], fig. 11).

Shell rough, ovate, very thick-walled, with subregular, circular pores of somewhat variable size. The diameter of the internal, simple, subspherical cavity is five to six times as great as the thickness of the wall. Mouth tubular, cylindrical, very narrow, only one-sixth as broad as the shell.

Dimensions.—Shell 0.16 long, 0.11 broad; mouth 0.02 broad.

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

Genus 530. Mitrocalpis,[[147]] Haeckel, 1881, Prodromus, p. 427.

Definition.—Archicorida with a double ovate or ellipsoidal shell, composed of two parallel lattice-plates, which are connected by numerous beams. Apex without horn.

The genus Mitrocalpis and the following closely allied Spongocyrtis differ from the four preceding genera of Archicorida in the complicated structure of the shell-wall, which in the former is double, in the latter spongy. The mouth is in both genera constricted, narrow, and the apex without a horn. Mitrocalpis has been derived probably from Cyrtocalpis in the same way as Peripyramis from Bathropyramis, by development of spines on the surface of the shell, which at equal distances from the latter become connected by branches, thus forming an outer envelope.

1. Mitrocalpis palliata, n. sp.

Shell ellipsoidal, large, one and a third times as long as broad. Inner shell very thin-walled, with irregular, polygonal pores of very variable size and form. From its nodal points there arise numerous bristle-shaped radial beams, about as long as the diameter of the mouth, which are connected at equal distances from the surface by delicate threads, forming the outer enveloping shell. The surface of the latter is smooth. The thin bars of the inner shell are twice to four times as broad as those of the outer. Mouth about one-seventh as broad as the shell, with a short tubular peristome.

Dimensions.—Shell 0.35 long, 0.27 broad; mouth 0.04, distance of both shells 0.037.

Habitat.—Central Pacific, Station 271, surface.

Genus 531. Spongocyrtis,[[148]] Dunikowski.

Spongocyrtis, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, vol. xlv. p. 31.

Definition.—Archicorida with a spongy ovate shell, the wall of which is composed of irregular spongy wickerwork. Apex without horn.

The genus Spongocyrtis differs from most other Monocyrtida in the spongy structure of the shell, which is found in only very few other genera of Cyrtoidea, e.g., in Spongopyramis and Spongomelissa. It has been derived either from the similar Cyrtocalpis by development of irregular spongy wickerwork on the surface of the simple lattice-shell; or from Arachnocalpis (Pl. [98], fig. 13) by loss of the peristome.

1. Spongocyrtis montis ovis, Dunikowski.

Spongocyrtis montis ovis, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, vol. xlv. p. 31, Taf. vi. figs. 67, 68.

Shell broad, ovate, rough, spongy, thick-walled; length to the breadth = 4 : 3. Spongy framework very dense and dark, with very small roundish pores. Mouth constricted, with a short tubular peristome, about one-third as broad as the shell.

Dimensions.—Shell 0.35 long, 0.26 broad; mouth 0.08 broad.

Habitat.—Fossil in the Alpine Lias (Schafberg bei Salzburg, Dunikowski).

2. Spongocyrtis arachnoides, n. sp.

Shell ellipsoidal, spiny, spongy, thin-walled; length to the breadth = 3 : 2. Spongy framework loose and delicate, with irregular polygonal meshes and arachnoidal thread-like bars. Mouth constricted, without peristome, about one-fifth as broad as the shell. (Very similar to Arachnocalpis ellipsoides, Pl. [98], fig. 13, but without corona around the mouth.)

Dimensions.—Shell 0.32 long, 0.21 broad; mouth 0.04 broad.

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

Subfamily 2. Archicapsida, Haeckel, 1881, Prodromus, p. 428.

Definition.—Cyrtocalpida, with the basal mouth of the shell fenestrated (vel Monocyrtida eradiata clausa).

Genus 532. Halicapsa,[[149]] Haeckel, 1881 Prodromus, p. 429.

Definition.—Archicapsida with an apical horn.

The genus Halicapsa, and the following closely allied Archicapsa, represent together the small subfamily of Archicapsida, or of those Cyrtocalpida, in which the basal mouth of the simple shell is closed by a lattice plate. This may be the original state of this family, if it is derived from the Circospyrida (Circospyris, Dictyospyris) by loss of the sagittal constriction and the primary ring. But it is also possible that the Archicapsida have been partly derived from the Archicorida by secondary fenestration of the open mouth. The genus Halicapsa may be easily confounded with the similar Ellipsid Lithapium (compare p. [303], Pl. [14], figs. 8-10). The skeleton of both genera may be perfectly similar, the only distinction being the structure of the central capsule, which in Halicapsa is that of the Monopylea, in Lithapium that of the Peripylea.

Subgenus 1. Calpocapsa, Haeckel.

Definition.—Surface of the shell smooth or rough, but not spiny.

1. Halicapsa lithapium, n. sp. (Pl. [97], fig. 6).

Shell pear-shaped, rough, one and a half times as long as broad. Pores subregular, circular, twice as broad as the bars. Basal plate with four larger ovate cortinar pores (two larger cardinal and two smaller jugular), and with six smaller peripheral pores (fig. 6). Horn of the apex three-sided pyramidal, stout, half as long as the shell.

Dimensions.—Shell 0.16 long, 0.1 broad; horn 0.08 long.

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

2. Halicapsa triglochin, n. sp. (Pl. [53], figs. 3, 4).

Shell ovate, rough, a little longer than broad. Pores regular, circular, hexagonally framed, of the same breadth as the bars. Basal plate (fig. 4) without larger pores. Horn pyramidal, stout, about half as long as the shell, with three short, horizontally divergent secondary spines at the base (possibly remnants of three original cortinar feet?)

Dimensions.—Shell 0.11 long, 0.09 broad; horn 0.06 long.

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

3. Halicapsa prunoides, n. sp.

Shell pear-shaped, tuberculate, a little longer than broad. Pores irregular, roundish, of different sizes. Basal plate with four larger and six smaller pores. Horn pyramidal, stout, about one-third as long as the shell. (May belong perhaps to the similar Prunoidea Lithapium, compare p. [303] and Pl. [14], figs. 8-10.)

Dimensions.—Shell 0.14 long, 0.12 broad; horn 0.05 long.

Habitat.—Fossil in Barbados.

Subgenus 2. Echinocapsa, Haeckel, 1881, Prodromus, p. 429.

Definition.—Surface of the shell spiny, covered with thorns, papillæ or larger spines.

4. Halicapsa papillata, n. sp.

Shell bottle-shaped, papillate, one and a half times as long as broad. Pores circular, much larger in the middle part than towards the poles. The elevated frames between them bear on the nodal points large blunt conical papillæ. Basal plate without larger pores. Horn three-sided pyramidal, one-third as long as the shell, gradually passing into the slender neck of the bottle.

Dimensions.—Shell 0.22 long, 0.15 broad; horn 0.07 long.

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

5. Halicapsa pyriformis, Haeckel.

? Haliomma pyriforme, Bailey, 1856, Amer. Journ. Sci. and Arts, vol xxii. p. 1, pl. i. fig. 29.

Shell pear-shaped, a little longer than broad, covered with numerous short conical spines. Pores subregular, circular, of nearly equal size, twice as broad as the bars. Basal plate with four crossed larger ovate pores (two larger cardinal and two smaller jugular pores). Horn stout pyramidal, scarcely one-fourth as long as the shell.

Dimensions.—Shell 0.16 long, 0.14 broad; horn 0.04 long.

Habitat.—Fossil in Barbados, living in the North Pacific (Kamtschatka)?

6. Halicapsa hystrix, n. sp. (Pl. [53], figs. 5, 6).

Shell pear-shaped, subspherical, a little longer than broad, with scattered stout pyramidal spines about as long as the radius of the shell. Pores subregular, circular, three times as broad as the bars. Basal plate (fig. 6) without larger pores. Horn very large, pyramidal, longer than the shell.

Dimensions.—Shell 0.1 long, 0.09 broad; horn 0.13 long.

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

Genus 533. Archicapsa,[[150]] Haeckel, 1881, Prodromus, p. 428.

Definition.—Archicapsida without apical horn.

The genus Archicapsa differs from the preceding Halicapsa in the absence of the apical horn, and represents the simplest form among the Monocyrtida clausa, a simple, ovate, or pear-shaped shell without any appendages. The characteristic structure of the basal lattice-plate (with three or four large cortinar pores) makes it probable that Archicapsa has been derived either from Halicapsa, by loss of the horn, or directly from Dictyospyris, by reduction of the sagittal ring and constriction.

1. Archicapsa triforis, n. sp. (Pl. [53], figs. 1, 2).

Shell pear-shaped, smooth, one and a half times as long as broad. Pores subregular, circular, of about the same breadth as the bars. Basal plate (fig. 2) with three very large pores, three times as broad as the others (one odd sternal pore and two paired cardinal pores).

Dimensions.—Shell 0.09 long, 0.06 broad.

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

2. Archicapsa quadriforis, n. sp.

Shell ovate, rough, a little longer than broad. Pores subregular, circular, twice as broad as the bars. Basal plate with four larger ovate cortinar pores (two smaller jugular and two larger cardinal pores).

Dimensions.—Shell 0.12 to 0.15 long, 0.1 to 0.12 broad.

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

3. Archicapsa nonaforis, n. sp.

Shell pear-shaped, thorny, one and a half times as long as broad. Pores regular, circular, small, hexagonally framed, twice as broad as the bars. Basal plate with nine cortinar pores (three larger alternating with three pairs of smaller pores, as in Pl. [87], fig. 2).

Dimensions.—Shell 0.14 long, 0.09 broad.

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