_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 {1186}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.