Page:Scientific results HMS Challenger vol 18 part 1.djvu/648

440 seven or nine) conical, half as long as the radius, twice as long as broad, without a connecting equatorial girdle.

Dimensions.—Diameter of the disk 0.17, of the medullary shell 0.04; length of the radial spines 0.04, basal breadth 0.02.

Habitat.—Fossil in Barbados.

7. Heliosestrum irregulare, n. sp.

Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish; nine to eleven on the radius. Eight conical radial spines of irregular size and distribution, often seven or nine, about as long as the radius of the disk (in some cases longer, in others shorter). No connecting equatorial girdle.

Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.1, basal breadth 0.02.

Habitat.—Central Pacific, Stations 270 to 272, depth 2425 to 2925 fathoms.

Definition.—Surface of the disk armed with radial spines. Bases of the marginal spines free, without a connecting equatorial girdle.

8. Heliosestrum octonum, n. sp. (Pl. 34, fig. 3).

Disk with spiny surface, three times as broad as the medullary shell. Pores circular, of very different sizes; eight to ten on the radius. Eight conical marginal spines of equal size and equidistant, as long as the radius of the disk, and one-third as broad at the base as the medullary shell. Numerous spines on the surface bristle-shaped, on the margin half as long as the eight main spines, in the central part shorter.

Dimensions.—Diameter of the disk 0.18, of the medullary shell 0.06; length of the marginal spines 0.1, basal breadth 0.02.

Habitat.—Central Pacific, Station 271, surface.

9. Heliosestrum ægineta, n. sp.

Disk with spiny surface, four times as broad as the medullary shell. Pores irregular, roundish, of different sizes; twelve to fourteen on the radius. Eight pyramidal marginal spines regularly disposed, four larger (perradial) alternating with four smaller (interradial); the former as long as the radius of the disk, the latter half as long.

Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the marginal spines 0.05 to 0.1, basal breadth 0.03.

Habitat.—South Atlantic, Station 330, surface.