Pteraster rugosus H. L. Clark 1941

Pteraster rugosus Clark

Pteraster rugosus H. L. Clark, 1941:61, pl. 6: fig. 1.

This nearly pentagonal species has a highly inflated disc and five short, broad arms which curve upward at the tip, so the end of the ambulacral groove is actually on the abactinal surface; the interradial arcs are wide and shallow. The dorsal membrane is thin, with numerous small spiraculae, and contains many small calcareous deposits. It is produced in a regular pattern of peaks by the underlying spines. The cruciform abactinal plates have long, Hat lobes and a tall pedicel, narrow at the base but expanded to a stout, ridged or grooved top which bears 5–8 spines, about as long as the pedicel and not particularly slender or acute. The central osculum is small and surrounded by a series of continuous spines about the same length as the paxillar spines. The actinal surface is plane and distinctive by reason of its 20–30 flat, closely set actinolateral spines whose square tips support a broad lateral fringe. The adambulacral furrow spines are erect and webbed, in a curved series; there are 4–6 spines (Clark says 5 or 6) and the inner one or two are small, but the others are long and not particularly slender or acute.

The mouth plates bear seven marginal spines, webbed together, on each half; the two at the apex of the plate are long and slender, and the others decrease gradually in length to a small spine at the outer edge of the margin. On the actinal face of the mouth plate is a single large, stout suboral spine, white at the base but hyaline at the tip. The tube feet are notably smaller and more delicate than those of most species of Pteraster. This species is distinctive because of its generally neat and regular appearance compared to other Pterasteridae. The largest specimen in the collection has an average of four adambulacral furrow spines, as compared to the 5 or 6 noted by Clark, but it is larger than Clark’s largest specimen, and is undoubtedly the same species; this may be a function of growth. The white color noted by Clark in live material is retained in preserved specimens.

The distribution presently known is from northern Cuba to the Leeward Islands, in 50–255 fathoms.

MATERIAL EXAMINED.—Oregon Stations: 4994 (1) [R=24 mm, r=17 mm, Rr=1:1.5]; 5937 (1) [R=12 mm, r=7 mm, Rr=1:1.8].