20. Theocapsa darwinii, n. sp. (Pl. [66], fig. 12).
Shell pear-shaped, with two distinct strictures. Length of three joints = 1 : 1 : 5, breadth = 1 : 2 : 5. Cephalis hemispherical, with a conical horn of twice the length. Thorax campanulate, with small, regular, circular pores. Abdomen broad, ovate, with larger, regular, circular, hexagonally-framed pores. Basal pole hemispherical.
Dimensions.—Length of the three joints, a 0.03, b 0.04, c 0.2; breadth, a 0.04, b 0.08, c 0.2.
Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms.
Genus 624. Tricolocapsa,[[241]] Haeckel.
Definition.—Theocapsida (vel Tricyrtida eradiata clausa) without apical horn, with a terminal lattice-plate on the mouth.
The genus Tricolocapsa differs from the preceding Theocapsa in the loss of the apical horn, and exhibits therefore to it the same relation that Theocampe bears to Theocorys. In some species (Pl. [66], figs. 1, 3) a small tube begins to be developed on the cephalis, and these may perhaps be separated as a peculiar genus, Tricolopera.
Subgenus 1. Tricolocapsula, Haeckel.
Definition.—Thorax of about the same size as the abdomen, or larger.
1. Tricolocapsa theophrasti, n. sp. (Pl. [66], fig. 1).