Subgenus 2. Diploconium, Haeckel.
Definition.—Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.
4. Diploconus fasces, Haeckel.
Mantle of the double cone compressed, with elliptical transverse section; its contour straight; its surface with numerous longitudinal furrows; its margin finely denticulated. Diameter of its mouth two-fifths as long as the whole shell and three times as broad as its equatorial diameter. The two main spines one-third longer than their conical sheath, four-edged. The eighteen smaller spines thick and short, cylindrical or a little compressed.
Dimensions.—Length of the shell 0.18; equatorial breadth 0.025, polar breadth 0.07.
Habitat.—Mediterranean (Messina), surface.
5. Diploconus cotyliscus, n. sp. (Pl. 140, fig. 4).
Mantle of the double cone compressed, thin walled, with elliptical transverse section; its contour convex; surface and margin nearly smooth. Diameter of its mouth half as long as the whole shell and twice as long as its equatorial diameter. The two main spines scarcely longer than their hemispherical sheath. The smaller spines conical, straight, nearly of the same length.
Dimensions.—Length of the shell 0.3; equatorial breadth 0.08, polar breadth 0.15.
Habitat.—Tropical Atlantic, Station 347, surface,
6. Diploconus saturnus, Haeckel.
Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour convex; its surface with numerous deep and irregular longitudinal furrows and marginal incisions. Diameter of its mouth one-third as long as the whole shell and twice as broad as its equatorial diameter. The two hydrotomical spines short, scarcely longer than their sheath. The eighteen other spines thin, cylindrical, nearly of the same length, curved. (Resembles a sheaf.)
Dimensions.—Length of the shell 0.24; equatorial breadth 0.04, polar breadth 0.07.
Habitat.—South Pacific, Station 300, surface.
7. Diploconus hexaphyllus, n. sp. (Pl. 140, fig. 2).
Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour straight; surface with six stronger and numerous smaller straight ribs and six marginal
