“PTERASTER RUGATUS, n. sp.
Marginal contour subpentagonal, interradial angles scarcely indented, the lesser radius being in the proportion of 68.4 per cent.; R=9.5 millim., r=6.5 millim. Interradial margin rounded, extremities of the radii slightly upturned, exposing the end of the furrow. Dorsal profile rounded, not high, tapering but little towards the extremities of the radii. Abactinal surface flat or slightly convex. Lateral fringe very slightly produced beyond the margin of the test.
Supradorsal membrane subcorragated, not reticulated. Paxillae-spinelets fine, about 5 or 6 in number; tips slightly protuberant, and producing a slight papillate appearance on the dorsal surface; no regularity of arrangement perceptible. Membrane indurated with minute spicules averaging .03-.04 millim. in length—small, irregular and angularly branching bodies, sub‑dendriform in appearance, fairly well spaced. The spiracula are rather large, not numerous, and are irregularly placed.
Ambulacral furrows narrow, uniform in breadth till near the extremity, not petaloid. Ambulacral suckers in regular simple pairs. Ambulacral spinelets short and rather robust, 3 to 4 in each comb, 3 only on the outer part of the ray. Innermost spine nearly as long as the others, or, if a small inner one is present, it is so aborted as to be invisible without dissection. Web remarkably thick and fleshy, subsaccular over the spinelets, passing off from the outermost spine with a long gentle sweep far out on to the lateral fringe.
Mouth-plates each bear on their margin about three rather short, robust mouth-spines webbed together. Secondary superficial mouth-spines one on each plate, perpendicular to the plane, longer than any of the other spines, exceedingly thick, triangular, translucent, sharply pointed, and covered with a thick fleshy investment.
Aperture-papillae large, prominent, subtriangular. Actinolateral spines directed horizontally, comparatively long, especially in the interbrachial space. Web rather thick and fibrous.
Colour, in alcohol, greyish white.
Station 150. Lat. 52° 4' S., long. 71° 22' E. Depth 150 fms.; bottom temperature 1.8°C.; rock.”
(Sladen, 1882: 192-193)
