Page:Scientific results HMS Challenger vol 18 part 1.djvu/749

Rh 4. Stauralastrum clavigerum, n. sp.

Arms twice as long as broad, in their distal half lenticular, nearly circular, twice as broad as in their square proximal half; their distal breadth equals the diameter of the central disk, which exhibits three to four rings. Edges of the arms concave.

Dimensions.—Radius of each arm 0.2, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Stauralastrum dilatatum, n. sp.

Arms of nearly equal length and breadth, at their convex distal end three times as broad as at their narrow base; their distal breadth three times as large as the radius of the central disk, which exhibits three to four rings. (Resembles Histiastrum quadrigatum, Pl. 46, fig. 3, but has no patagium.) Edges of the arms concave.

Dimensions.—Radius of each arm 0.15, basal breadth 0.04, terminal breadth 0.12.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Definition.—Ends of the arms with one or more terminal spines.

6. Stauralastrum rhopalophorum, n. sp. (Pl. 45, fig. 1).

Hagiastrum rhopalophorum, Haeckel, 1881, Prodromus, p. 460.

Arms cylindrical, eight times as long as broad at their base, at their distal end club-shaped, three times as broad as at their base; their distal breadth twice as large as the diameter of the central disk, which exhibits two to three rings. Surface thorny, with larger spines towards the end, and one radial, very strong, angular terminal spine. Edges of the arms parallel.

Dimensions.—Radius of each arm (without terminal spine) 0.32, basal breadth 0.03, terminal breadth 0.1.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

7. Stauralastrum antiquum, n. sp.

Rhopalastrum sp. Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 5.

Arms six times as long as broad at their base, in their distal half nearly spherical, three times as broad as in their cylindrical basal half; their distal breadth nearly equals the diameter of the central disk which exhibits three to four rings. On the end of each arm one strong, angular, terminal spine. (Differs from the preceding species by larger central disk and stouter arms, also by less developed spines.) Edges of the arms parallel.

Dimensions.—Radius of each arm 0.25, basal breadth 0.04, terminal breadth 0.12.

Habitat.—Fossil in the Barbados rocks; and living in the depths of the Central Pacific, Station 266, depth 2750 fathoms.