“HYMENASTER CRUCIFER, n. sp.
Marginal contour subpentagonal; interradial angles very slightly indented, the lesser radius being in the proportion of 66.6 per cent.; R=51 millim., r= 34 millim. Radii tapering to a fine extremity, which is somewhat attenuated and produced. Marginal fringe comparatively insignificant as seen from above, and narrowing rapidly towards the extremity of the rays. Form depressed, more convex on the actinal than on the abactinal surface.
Supradorsal membrane rather thin, muscular fibres numerous, thick, and radiating regularly from the tips of the spinelets. Paxillae numerous, though somewhat widely spaced, bearing a crown of four or sometimes five spinelets, which usually elevate the membrane into slightly raised, Maltese-cross-shaped areas. The spinelets are sharply prominent; and the fibres for a short distance around the tip are merged together and form a homogeneous "cap;" the caps of each of the spinelets of a crown coalesce, and thus produce the subcruciform or rhomboid elevations above mentioned. The paxillae are well spaced, and are arranged in longitudinal lines along the rays. No spiracula occur on the raised areas; but in the intermediate spaces they are very numerous and closely placed, the intervals between the thick radiating bands being very narrow, and occupied by a great number of small spiracula placed close together in line, 4 to 8, or even more in each, and separated from one another by only the finest dissepiment. The numerous spiracula and the isolated unpunctured cruciform areas give a striking character to the dorsal surface. The oscular orifice is large, the valves all webbed together, and the spinelets quite hidden in membrane, the whole of which is uniformly punctured with a great number of small spiracula, not quite so closely placed as those on the disk, and not arranged in lines.
Ambulacral furrows rather widely petaloid, rapidly constricted at the extremity. Ambulacral spines three, short, nearly uniform in length, pointed, and covered with a membrane expanded into a lanceolate shape, but with no terminal saccular prolongation. Each series of spines is placed diagonally upon its plate, or oblique to the line of the furrow. Aperture-papillae large and broadly subspatulate or even subrhomboid, expanded somewhat obliquely, the pedicel seeming to be attached rather on one side.
Mouth-plates rather broad, prominent aborally, having 5 or 6 short mouth-spines attached to the lateral aliform extensions, and directed horizontally. Two short, robust, subconical secondary mouth-spines are borne on the superficies of each plate—one near the adoral extremity, and the other, which is thickest, placed midway between this spine and the aboral extremity of the mouth-plate.
Actino-lateral spines long and well spaced, about 40 on each side of a furrow, the 11th or 12th from the mouth being longest. The spines within the disk do not quite meet in the median inter-radial line; and those along the outer third of the ray diminish in length very rapidly; they are, however, rather irregular in their length throughout, which gives a ragged appearance to the fringe. The spines are pointed at their extremity; and the web is very slightly indented between.
Colour, in alcohol, yellowish grey.
Station 158. Lat. 50° 1' S., long. 123° 4' E. Depth 1800 fms.; bottom temperature 0.3° C.; Globigerina-ooze.”
(Sladen, 1882: 227-228)
