Page:Scientific results HMS Challenger vol 18 part 1.djvu/1096

888 The two hydrotomical spines very thick and short, pyramidal, little prominent. Short rudiments of the eighteen other spines present, bristle-shaped.

Dimensions.—Length of the shell 0.1, breadth 0.05.

Habitat.—South Atlantic, Station 335, surface.

Definition.—Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.

3. Diplocolpus serratus, n. sp. (Pl. 140, fig. 5).

Mantle of the double cone thick walled, compressed, with elliptical transverse section; its surface with numerous delicate ribs; contour little convex; margin regularly serrate. Hydrotomical spines short, pyramidal, with six serrate wings. Transverse diameter of the shell nearly twice as great at the polar mouth as at the equator and half as long as the whole shell.

Dimensions.—Length of the shell 0.15; breadth on the equator 0.035, on the poles 0.07.

Habitat.—Central Pacific, Station 274, surface.

4. Diplocolpus dentatus, n. sp. (Pl. 140, fig. 9).

Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with six deeper and numerous shallower furrows; margin denticulated, with six triangular prominent larger teeth. Hydrotomical spines very large prismatic, pyramidal at the ends. Transverse diameter of the shell a little larger at the polar mouth than at the equator and half as long as the whole shell.

Dimensions.—Length of the shell 0.2; breadth on the equator 0.08, on the poles 0.1.

Habitat.—North Pacific, Station 244, surface.

5. Diplocolpus sulcatus, n. sp. (Pl. 140, fig. 8).

Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with twelve to sixteen deep longitudinal furrows, which are separated by thin, undulating, double edged ribs; margin little dentated. Hydrotomical spines short, pyramidal, with six dentate wings. Transverse diameter of the shell a little larger at the polar mouth than at the equator, about one-third of the whole length of the shell.

Dimensions.—Length of the shell 0.17; breadth on the equator 0.05, on the poles 0.06.

Habitat.—South Pacific, Station 291, surface.