Page:Scientific results HMS Challenger vol 18 part 1.djvu/686

478 1. Stauractura octogona, n. sp.

Phacoid shell twice as broad as the medullary shell, with eight pores in its radius. Arms nearly square, little larger than the phacoid shell, with broad truncated distal ends. The corners of the latter are so connected by the complete patagium, that the whole shell forms a regular octagon.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.12, distal breadth 0.11.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

2. Stauractura tetragona, n. sp.

Phacoid shell three times as broad as the medullary shell, with eleven pores on its radius. Arms club-shaped, nearly as long as the diameter of the phacoid shell, and one and a half times as long as broad at the distal part; at the distal end rounded, blunt, without terminal spine. The terminal points of the arms are so connected by a thin, complete patagium, that the whole shell becomes a regular square.

Dimensions.—Diameter of the phacoid shell 0.13, of the medullary shell 0.045; length of the arms 0.12, greatest breadth 0.08.

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

Definition.—Distal end of the arms furnished with a radial spine.

3. Stauractura medusina, n. sp.

Phacoid shell two and a half times as broad as the medullary shell, with nine pores on its radius. Arms club-shaped, one and a half times as long as the diameter of the phacoid shell, and in the outer third nearly as broad as the latter, at the base scarcely one-third as broad; their truncated distal end armed with a strong pyramidal terminal spine. Patagium incomplete, enveloping only the basal half of the arms, with three rectilinear parallel rows of chambers, forming a square.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.04; length of the arms 0.14, greatest breadth 0.08.

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

4. Stauractura quadrata, n. sp.

Phacoid shell twice as broad as the medullary shell, with seven pores on the radius. Arms nearly square, about as large as the phacoid shell, with a strong pyramidal terminal spine at the distal end. Patagium complete, between every two arms triangular, with rectilinear parallel