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.