Page:Scientific results HMS Challenger vol 18 part 1.djvu/1083

Rh 1. Hexalaspis heliodiscus, n. sp. (Pl. 139, fig. 2).

All six hydrotomical spines of nearly equal size (or sometimes the two equatorial a little larger than the four polar spines), isosceles triangular, compressed, smooth; about as long as the radius of the shell, and half as broad at the base. The fourteen other spines very small, also triangular and compressed, but little prominent on the two convex sides of the lenticular shell.

Dimensions.—Diameter of the shell 0.11; length of the six hydrotomical spines 0.05, basal breadth 0.03.

Habitat.—Central Pacific, Station 271 to 274, surface.

2. Hexalaspis stellata, n. sp.

All six hydrotomical spines of nearly equal size, lanceolate compressed, with two longitudinal furrows on each flat side, about as long as the diameter of the shell, and one-fourth as broad at the base. The fourteen other spines very thin, also compressed, half as long and only one-fourth as broad as the six large spines.

Dimensions.—Diameter of the shell 0.14; length of the six hydrotomical spines 0.13, basal breadth 0.035.

Habitat.—South Pacific, Station 284, surface.

Definition.—Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.

3. Hexalaspis sexalata, n. sp.

Six hydrotomical spines of unequal size; the two equatorial spines about as long as the shell-radius and twice as long as the four polar spines, which are isosceles triangular. The fourteen other spines are only half as long and one-fourth as broad as the latter, little prominent. (Resembles Hexonaspis hastata, Pl. 140, fig. 16, which is distinguishable by the furrows on the six spines and by the total absence of the fourteen external rudimentary spines.)

Dimensions.—Diameter of the shell 0.15; length of the two equatorial spines 0.08, of the four polar spines 0.04, of the fourteen other spines 0.02.

Habitat.—North Pacific, Station 240, surface.

4. Hexalaspis hexalastrum, n. sp.

Six hydrotomical spines of unequal size; the two equatorial spines somewhat longer than the diameter of the shell and three times as long as the four polar spines, all six triangular, smooth, of the same basal breadth (equal to half the radius). The fourteen other spines very thin, conical at the base, nearly as long as the radius.