10. Sethoconus nassa, Haeckel.
Cephalis slenderly ovate, with sharp collar stricture, few scattered pores, and a very stout, pyramidal horn of the same length, which is surrounded at the base by three short, divergent, ascending spines (perhaps the remnants of the three cortinar rods of Eucecryphalus, &c. ?). Thorax slender, conical, with straight outlines, and small, dense, regular, circular pores of equal size.
Dimensions.—Cephalis 0.04 long, 0.02 broad; thorax 0.12 long, 0.08 broad.
Habitat.—Fossil in Barbados.
11. Sethoconus tabulatus, Haeckel.
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.
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.
Dimensions.—Cephalis 0.005 diameter, thorax 0.12 long, 0.05 broad.
Habitat.—Indian Ocean, Zanzibar, depth 2200 fathoms (Pullen).
13. Sethoconus verrucosus, Haeckel.
Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the
