Cephalis spherical, very small, with two divergent conical horns of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 5, breadth = 1 : 5. Thorax spherical, with regular, circular, hexagonally-framed pores. From the collar stricture arise three radial internal beams, horizontally diverging, and inserted at the inside of the thorax.
Dimensions.—Cephalis 0.03 diameter; thorax 0.15 diameter.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
5. Lithopera gutta, Ehrenberg.
Lithopera gutta, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 2.
Shell pear-shaped, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis spherical, with a conical horn of the same length; its lower half hidden in the uppermost part of the ovate thorax, and connected with its wall by three internal, cortinar beams. Pores of the thorax very irregular in form and size, partly lobed.
Dimensions.—Cephalis 0.02 diameter; thorax 0.08 long, 0.06 broad.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms; Philippine Sea (depth 3300 fathoms), Ehrenberg.
Genus 552. Micromelissa,[[169]] Haeckel, 1881, Prodromus, p. 433.
Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent, solid, lateral wings. Cephalis with a horn.