ASTEROIDEA OF H.M.S ' CHA.LLE]SraER' EXPEDITIOjST. 229 



less imperfectly closed along the suture and widely open at tlie 

 aboral extremity. A single, short, conical, sharply pointed 

 mouth-spine to each mouth-angle stands at the innermost point 

 and in the median line. Two large segmental papillae occupy 

 nearly the whole of the lateral portion of each mouth-plate ; 

 they stand close together, touching one another, and the aboral 

 one is the larger of the two. 



The actinal interbrachial areas are small ; and the squamous 

 plates are comparatively few in number, these being rather large 

 in the immediate angle, though very narrow and elongate 

 near the margin. 



Colour, in alcohol, greyish white, excepting the dorsal mem- 

 brane, which is bluish grey. 



Station 298. Lat. 34° 7' S., long. 73° 56' W. Depth 2225 

 fms. ; bottom temperature l°-3 C. ; grey mud. 



Stteacastee, n. gen. 



Rays five, long and attenuate, incapable of being reverted. Supero- 

 marginal plates meet in the median dorsal line, encasing the ray, and bear 

 long, robust, cylindro-conical spines which form a single series along the 

 median dorsal line. Abactinal area covered with membrane, beset with 

 simple spiuiferous spicules or with pseudo-paxillse. No specially developed 

 epiproctal protuberance. Actinal interradial area paved with thin, smooth 

 plates, arranged in regular columns, more or less clearly imbricating, and 

 covered with a delicate membrane. Ambulacral furrows narrow and moi'e 

 or less enclosed. Ambulacral spines elongate, needle-shaped, and with a 

 tendency to radiate apart. Cribriform organs three to seven in number 

 in each angle. 



Stteacastee. hoeeidus, n. sp. 



Eays five, very long and slender, compressed laterally, and 

 tapering to the extremity. The interbrachial angle is very wide, 

 and its rounding is more or less obliterated by the subpentagonal 

 character of the disk. The lesser radius is in the proportion of 

 20 per cent.; 11 = 75 millim., r=15 millim.; B=6r. The disk 

 is not high, although capable of being inflated to a slight extent 

 above the level of the marginal plates. Dorsal area covered 

 with a leathery integument, beset with minute, compact, and 

 closely crowded pseudo-paxillee of 4-8 spinelets, occupying the 

 whole area. The paxillse are smaller in the immediate centre of 

 the disk, but there is no special protuberance. The actinal 



