Page:Scientific results HMS Challenger vol 18 part 1.djvu/1085

Rh 2. Hexaconus coronatus, n. sp. (Pl. 139, fig. 5).

All six hydrotomical spines of equal size, conical, somewhat compressed, with two prominent edges, scarcely as long as the radius of the shell. Sheaths crested, strongly dentated on the mouth, three times as broad as long and only one-sixth as long as the spines. Fourteen smaller spines about half as large as the six principal spines, of the same form, but without coronated sheaths.

Dimensions.—Diameter of the shell 0.2; length of the six hydrotomical spines 0.1; basal breadth 0.02.

Habitat.—North Pacific, Station 253, surface.

3. Hexaconus velatus, n. sp. (Pl. 139, fig. 6).

All six hydrotomical spines of equal size, conical, somewhat compressed, shorter than the radius of the shell. Sheaths very large, truncated conical, enveloping the spines almost entirely, with crested wall, only half as broad at the constricted mouth as at the base. The fourteen smaller spines about half as large as the six principal spines, of the same form, but without large sheaths.

Dimensions.—Diameter of the shell 0.12; length of the six hydrotomical spines 0.05; basal breadth 0.01.

Habitat.—North Atlantic, Station 354, surface.

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

4. Hexaconus serratus, n. sp. (Pl. 139, fig. 4).

Six hydrotomical spines of unequal size, the two equatorial being as long as the radius of the shell and one and a half times as large as the four polar; all of the same form, triangular, compressed, with six prominent edges. Sheaths cylindrical, half as long as the spines, with prominent crests, and with strong serrated teeth at the distal mouth. The fourteen smaller spines scarcely one-fourth or one-sixth as large as the six principal spines, without prominent sheaths.

Dimensions.—Diameter of the shell 0.2; length of the equatorial spines 0.1, basal breadth 0.05; length and breadth of the sheaths 0.05.

Habitat.—South Pacific, Station 288, surface.

5. Hexaconus vaginatus, n. sp. (Pl. 139, fig. 7).

Six hydrotomical spines of unequal size; the two equatorial very stout, pyramidal, six-edged, nearly as long as the diameter of the shell, and on the base three to four times as broad as the eighteen other spines, which are much thinner, all nearly of equal length, and two-edged. All