E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Gephyreaster swifti is star shaped with small, tightly packed aboral paxillae and obvious granule-covered marginals. The aboral side is pink-orange and the oral side is paler. It has five arms up to 21 cm long, and an arm-to-disc ratio of 2.1 to 2.6. Rich Mattison of Juneau, Alaska, brought me a live specimen of G. swifti that was 41.5 cm in diameter. The aboral paxillae are closely packed and crowned with numerous granuliform spinelets. Between the paxillae, and almost hidden by them, are 1 to 3 papulae. The marginals are conspicuous and rounded, with a definite groove between infero- and superomarginals. The oral interradial area has oblong plates covered with coarse spinelets that lie in rows between the inferomarginals and corresponding adambulacrals. The adambulacrals have 2 or 3 furrow spines that almost cover the ambulacral furrow; and the oral surface has two or three transverse rows of 5 or 6 spines. The mouth plates are prominent, with numerous small blunt spines on the oral surface and numerous marginal spines in a series progressing to a single large apical spine.

Gephyreaster swifti is never vermilion like Mediaster aequalis, which is similar in shape but has smoother marginals that encroach much more on the aboral surface. Pseudarchaster alascensis is flatter, smoother and its arms tape