Page:Scientific results HMS Challenger vol 18 part 1.djvu/1084

876 Dimensions.—Diameter of the shell 0.21; length of the two equatorial spines 0.24, of the eighteen others 0.08 to 0.1; basal breadth of the six larger spines 0.05, of the fourteen others 0.01.

Habitat.—Western Tropical Pacific, Station 224, surface.

5. Hexalaspis hexaglypha, n. sp.

Six hydrotomical spines of unequal size; the two equatorial very large, six-sided prismatic, twice as long as the diameter of the shell and four times as long as the four pyramidal polar spines; each of these six spines with six deep furrows between the six prominent edges. The fourteen other spines very thin, compressed, two-edged, about as long as the radius of the shell.

Dimensions.—Diameter of the shell 0.11; length of the two equatorial spines 0.2, of the eighteen others 0.04 to 0.06; basal breadth of the six larger spines 0.03, of the fourteen others 0.01.

Habitat.—Tropical Atlantic, Station 352, surface.

Definition.— with twenty prominent radial spines, which are surrounded at the base by prominent sheaths; the six hydrotomical spines much larger than the fourteen others.

The genus Hexaconus differs from the preceding Hexalaspis in the development of conical or cylindrical sheaths surrounding the basal parts of the radial spines; these sheaths are developed sometimes around all twenty spines, sometimes only around the six larger hydrotomical spines.

Definition.—Six hydrotomical spines of equal size.

1. Hexaconus ciliatus, n. sp. (Pl. 139, fig. 3).

All six hydrotomical spines of nearly equal size, pyramidal, with six prominent edges, somewhat longer than the radius of the shell. Sheaths sulcated, finely ciliated at the mouth, twice as broad as long and only one-fourth as long as the spines. The fourteen smaller spines very thin, bristle-shaped, shorter than the radius of the shell.

Dimensions.—Diameter of the shell 0.16; length of the six hydrotomical spines 0.11; basal breadth 0.03.

Habitat.—Central Pacific, Station 270, surface.