Shell ovate, spinulate and costate, nearly twice as broad as long. Surface with fifteen to twenty prominent longitudinal ribs, which are convergent towards each pole and elegantly denticulate. The deep furrows between them are divided by delicate, parallel, transverse ribs into numerous short and broad dimples (thirty to forty in each furrow); each dimple contains a small pore, like a transverse fissure. The apex bears a short and stout, three-sided pyramidal horn, the hollow base of which is closed by a small cortinar septum with three collar pores (fig. 8b). This seems to indicate a rudimentary cephalis and the derivation of this species from Lychnocanium (Pl. [61]). Peristome constricted, only one-fourth as broad as the shell, with three short, conical, nearly vertical feet. The central capsule (fig. 8a) in the specimen examined was well preserved, hemispherical, not lobate, and filled up the upper half of the shell-cavity (beyond the rudiment of the cortinar septum).
Dimensions.—Shell 0.2 long, 0.12 broad; horn 0.01 long, feet 0.02 long.
Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.
7. Tripilidium elongatum, n. sp.
Shell elongate, smooth, nearly cylindrical, in the upper third conical. Pores small and numerous, regular, circular, half as broad as the bars, disposed in about thirty longitudinal alternating rows. Peristome scarcely constricted. The apical horn and the three parallel feet are of equal size and similar form, straight, conical, one-sixth as long as the shell.
Dimensions.—Shell 0.12 long, 0.06 broad; horn and feet 0.02 long.
Habitat.—Fossil in Barbados.
Subgenus 2. Tripodocorys, Haeckel, 1881, Prodromus, p. 428.
Definition.—Feet forked or branched.
8. Tripilidium dichopodium, n. sp.