Cornutella clathrata, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 39a, b, c.
Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the length. Thorax slenderly conical, three to four times as long as broad, smooth, with curved axis and small, regular, circular pores, nearly equal in size. This common species differs from all others of the genus by the curvation of the axis of the shell, which is more or less crescentic, or curved like a cowherd's horn; it may, therefore, represent a peculiar genus, Sethodrepanum.
Dimensions.—Cephalis 0.003 to 0.006 diameter, thorax 0.08 to 0.16 long, 0.03 to 0.05 broad.
Habitat.—Cosmopolitan; Atlantic, Pacific, many stations; fossil in Barbados and Sicily.
Subgenus 3. Phlebarachnium, Haeckel (et Cladarachnium, Haeckel), 1881,
Definition.—Cephalis small, with very small pores, and internal collar septum. Thorax spiny or thorny.
21. Sethoconus facetus, n. sp. (Pl. [55], fig. 1).
Phlebarachnium facetum, Haeckel, 1881, Prodromus, p. 430.
Cephalis small, hemispherical, with distinct collar septum, the same network as the thorax, and numerous bristle-shaped horns of the same length. Thorax wide, conical, about as long as broad, with slightly convex outlines; its network extremity delicate, with very small and numerous, regular, hexagonal pores, disposed in numerous divergent, longitudinal series, which are convoluted somewhat spirally around the shell axis. Surface covered with thin, scattered, bristle-shaped spines, about as long as the cephalis.
Dimensions.—Cephalis 0.02 diameter, thorax 0.2 long, 0.22 broad.