240 TTIE VOYAGE OF H.M.S. CHALLENGER. 



1. Bathybiaster loripes, n. sp. (PI. XXXVI. figs. 1 and 2 ; PI. XLII. figs. 1 and 2). 



Pays five. E = 82 mm., r = 14 - 5 mm. R> 5"5 r. Breadth of a ray near the base 

 (between the third and fourth supero-marginal plates), 15 mm. 



Rays moderately elongate, tapering continuously from the base to a finely pointed 

 extremity. Lateral walls high and nearly vertical. Interbrachial arcs acutely rounded. 

 Abactiual surface slightly inflated over the disk, and very slightly convex along the rays. 

 Actinal surface of the rays convex and merging gradually into the lateral wall, which 

 gives the rays a distinctly cylindrical appearance when viewed from below. On the other 

 hand, when seen from above they appear more or less flat in consequence of the small 

 degree of convexity of the abactiual area. 



The abactinal surface of the disk and rays is covered with numerous rather small and 

 closely crowded paxillse. These are low and of uniform height throughout, and consist of 

 seven to twelve small, very short, clavate or flaring, skin-covered, papilliform spinelets 

 — one or two irregularly central, and the whole forming a more or less compact and flat- 

 topped group. Often two or three thinner and more delicate spinelets may be seen on the 

 outside of the group. The paxillse diminish in size in the central area of the disk, and in 

 the immediate centre become extremely small and indistinguishable as separate paxillse ; 

 there is also a more or less strongly marked tendency to develop a conical prominence 

 in the centre of the abactinal area. The paxillse gradually diminish in size as they pro- 

 ceed along the ray, and become very small at the extremity. A more or less clearly 

 defined arrangement in transverse lines is discernible at the sides of the paxillar area 

 along the ray, but along the median line no order can be made out, nor are the paxillse 

 there distinguished by any difference in size. 



The supero-marginal plates, sixty-two in number from the median interradial line to 

 the extremity, are confined entirely to the lateral wall of the ray ; they are high and short, 

 the height being more than twice the length. On the inner part of the ray the height is 

 even three times the length and sometimes more. The surface of the plates is covered with 

 small, uniform, squamiform papillae, covered with membrane, which are more or less 

 closely appressed to the surface, their direction being upward, or towards the abactinal 

 surface ; and the squamules along the margins of the plate have a slight inclination over 

 the suture-line, which is thus emphasised superficially. At the extreme abactinal edge of 

 the plate is a short, conically-outlined but flat and squamule-like spinelet, very little 

 longer than broad, which is directed perpendicularly to the plane of the abactinal surface, 

 and to which this series of spinelets forms a well-defined boundary. 



The infero-marginal plates correspond exactly to the superior series, their length is the 

 same and their height subequal to those above described, or slightly less on the inner part 

 of the ray. The surface of the plates is covered with squamule-like papillse similar to those 

 on the supero-marginal plates, and there is a similar small, short, flat, pointed and squamule- 

 like spinelet close to the abactinal edge of the plate ; the series of these forming along 



