11. Sethoconus tabulatus, Haeckel.
Cycladophora tabulata, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. iv. fig. 18.
Cephalis subspherical, with slight collar stricture, and numerous small, irregular pores, without horn, or with a small conical horn. Thorax slenderly conical, with straight outlines, and large, regular, hexagonal pores. Mouth truncate. (In the specimen I examined the thorax was longer and more conically dilated; the cephalis had a distinct small horn.)
Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.06 broad.
Habitat.—North Atlantic, Antilles, depth 1600 fathoms (Ehrenberg); Station 347, depth 2250 fathoms.
Subgenus 2. Cornutellium (vel Ceratarachnium), Haeckel, 1881, Prodromus, p. 430.
Definition.—Cephalis very small, rudimentary, hyaline, without distinct collar septum, and without pores (or with scarce, rudimentary pores). Thorax smooth.
12. Sethoconus hexagonalis, Haeckel.
Cornutella trochus, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 287, Taf. ix. fig. 14.
Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the length. Thorax slenderly conical, or bottle-shaped, twice to three times as long as broad; in the lower half nearly cylindrical, with very thin, thread-like bars, and regular, hexagonal pores, increasing in size towards the mouth.