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).