Shell horn-shaped, slenderly conical, with curved, nearly semicircular axis, without external strictures, but with twelve to twenty internal septal rings. All joints nearly of the same length, the twelfth twice as broad as the third. On each joint three to four transverse rows of subregular, small, hexagonal pores. Horn of the cephalis conical, curved, of twice the length.
Dimensions.—Length of the curved axis of the shell (with sixteen joints) 0.32, length of each joint 0.02; breadth of the third joint 0.02, of the twelfth 0.04.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
Subgenus 3. Cyrtostrobus, Haeckel.
Definition.—Shell conical (often more campanulate or irregular), with straight axis; joints of different lengths. Cephalis not lobate.
11. Lithostrobus conulus, n. sp. (Pl. [80], fig. 1).
Shell slenderly conical, smooth, with straight axis, and seven to ten distinct strictures. Joints of different lengths; the fourth and fifth about twice as long as the preceding and following joints, the former with four to five, the latter with two to three transverse rows of large irregular pores; the seventh joint twice as broad as the third. Horn of the cephalis short, pyramidal.
Dimensions.—Length of the shell (with eight joints) 0.14, length of the fifth joint 0.03; breadth 0.06.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
12. Lithostrobus picus, Bütschli.