Habitat.—Fossil in Barbados.
Subfamily 2. Theocapsida, Haeckel, 1881, Prodromus, p. 436.
Definition.—Theocyrtida with the basal mouth of the shell fenestrated (vel Tricyrtida eradiata clausa).
Genus 623. Theocapsa,[[240]] Haeckel, 1881, Prodromus, p. 436.
Definition.—Theocapsida (vel Tricyrtida eradiata clausa), with an apical horn, and a terminal lattice-plate on the mouth.
The genus Theocapsa, and the two following genera, represent together the small subfamily of Theocapsida, or of those Tricyrtida in which the mouth is closed by a lattice-plate, and external radial appendages are wanting. Theocapsa may be derived from Theocorys by fenestration of the constricted mouth.
Subgenus 1. Theocapsetta, Haeckel.
Definition.—Thorax of about the same size as the abdomen, or somewhat larger; pores of both nearly equal in size and similar in form.
1. Theocapsa aristotelis, n. sp. (Pl. [66], fig. 6).
Shell subovate, smooth, with two distinct strictures. Length of the three joints = 2 : 6 : 7, breadth = 3 : 8 : 8. Cephalis hemispherical, with a conical, slender horn of about the same length. Thorax and abdomen nearly equal in size, thin-walled, smooth, with small, regular, circular pores of equal size. Basal pole rounded.