ASTEEOIDEA OF H.M.S. ' CHALLENGER ' EXPEDITIOK. 215 



Station 158. Lat. 50° 1' S., long. 123° 4' E. Depth 1800 fms. ; 

 bottom temperature 0°'3 C. ; Glohigerina-ooze. 



HtmEKASTEE PEE&AMEKTACEirs, n. Sp. 



Marginal contour stellato-pentagonal ; interradial angles mo- 

 derately indented, although the actual angle is masked by an 

 abnormal development of the actino-lateral spines, which meet 

 there and form a peak, and an irregular excrescence of the web. 

 The minor radial proportion is about 60'5 per cent. ; i2=66milliui., 

 r=40 millim. approx. The radial areas are well defined from the 

 lateral fringe, and taper rapidly at the extreme tip to a fine, 

 slightly produced extremity, which is recurved. The "fringe" is 

 more or less irregular, owing to the thickeniDg at the margin 

 and abnormal growth, and is only slightly indented or festooned 

 between the spinelets, the tips of which are rounded and 

 thickened. 



Supradorsal membrane thin, smooth and vellum-like. Paxillae 

 comparatively few in number, bearing 5 to 8 spinelets, which are 

 robust and widely expanded. Although these are in a certain 

 sense regular in their distribution over the area, no definite pat- 

 tern of arrangement is produced. The extremities of the spine- 

 lets do not protrude through the membrane, but simply elevate it 

 into small eminences ; and, owing to the thinness of the supra- 

 dorsal membrane, the outlines of the spinelets which form each 

 paxilla may be more or less clearly discerned. The radii are well 

 defined ; and no paxillse-spinelets occur in the immediate inter- 

 brachial portion of the lateral fringe, nor do any spinelets encroach 

 upon a narrow clear space which runs down the median line of 

 each radius. The fibrous bands are very numerous and closely 

 massed together ; indeed so great is their development that nearly 

 all individuality of fascicular character is obliterated and they 

 appear to form a compact muscular tissue. In certain lines, how- 

 ever, along the sides of the rays there seems to be a tendency 

 towards a greater and more definite development of fibres in a 

 lineal direction, parallel with the median line of the ray. The 

 spiracula are very few in number, quite microscopic, and occur 

 in little groups of 6 to 10 which are widely and irregularly distri- 

 buted. The oscular orifice is large, the valves when closed forming 

 a cone of small elevation ; and the spines which compose them 

 are somewhat irregular both in number and gradation in size. 



JAWS. JOUEN. — ZOOLOGY, TOL. XVI. 15 



