Page:Scientific results HMS Challenger vol 18 part 1.djvu/688

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Definition.— with five chambered arms on the margin of the circular or pentagonal disk, connected by a spongy patagium.

The genus Echinactura differs from the foregoing Pentactura in the patagium between the arms, and bears therefore the same relation to it as Pentinastrum in the Porodiscida does to Pentalastrum.

1. Echinactura culcita, n. sp.

Phacoid shell pentagonal, three times as broad as the medullary shell, with nine pores on its radius. Arms egg-shaped, about as long as the diameter of the phacoid shell, and in the distal part half as broad. The blunt ends of the arms are so connected by the complete patagium that the whole shell becomes a regular pentagonal disk.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.035; length of the arms 0.11, basal breadth 0.04, distal breadth 0.06.

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

2. Echinactura asteriscus, n. sp.

Phacoid shell twice as broad as the medullary shell, with seven pores on its radius. Arms lanceolate, twice as long as the diameter of the phacoid shell, in the middle part nearly as broad as the latter, at the distal end with a strong conical terminal spine. Patagium incomplete, enveloping only the basal half of the arms.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.045; length of the arms 0.2, greatest breadth 0.08.

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

3. Echinactura goniaster, n. sp.

Phacoid shell three 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, in the distal part nearly as broad as the latter, in the basal part one-third as broad; at the end a strong pyramidal spine. Patagium nearly complete, with concave dentated margin between each pair of arms, therefore the pentagonal disk of the whole shell with concave sides.

Dimensions.—Diameter of the phacoid shell 0.12, of the medullary shell 0.04; length of the arms (without terminal spine) 0.18, basal breadth 0.04, distal breadth 0.1.

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