ASTEEOIDEA OF H.M.S. ' CHALLENaEE, ' EXPEDITION. 209 



angles to the line of junction of the moutli-plates. The anterior 

 pair are situated at a little distance from the adoral extremity of 

 the plates ; and the second pair, which are slightly larger and 

 rather wider apart, stand midway between them and the aboral 

 extremity of the month-plates. Immediately above the anterior 

 pair and placed on tlie innermost part of the lateral flanges, are a 

 pair of mouth-spines (/. e. one on each plate), similar in every 

 respect to tbe secondary spines just described, only slightly 

 smaller and rather wider apart ; indeed, in some specimens one 

 is almost inclined to class them along witb the secondary series. 

 Midway on the horizontal margin of the flange is one small 

 pointed mouth-spine ; and in a large specimen a second and 

 rather larger spinelet occurs between this and the innermost 

 mouth-spine, and nearer to the latter. 



Actino-lateral spines rather robust, well-spaced, tapering slightly 

 at the tips, excepting those spines included within the inter- 

 brachial angle, which are slightly thickened and do not meet 

 their corresponding spines from the neighbouring ray in the 

 median interradial line. There are 25 to 27 actino-lateral spines 

 on each side of a furrow, the 7th or 8th from the mouth being 

 longest ; after this they gradually diminish in size as they pro- 

 ceed outward, maintaining, however, a fair length even at the 

 extremity, where they are little shorter than the first (or adoral) 

 spine of the series, thus forming a conspicuous little fringe round 

 the extremity of the ray. The ambulacral furrow is extended 

 vertically up the extreme tip o£ the ray, but is not exposed on 

 the dorsal surface, being arched over by the terminal spinelets 

 just described. Immediately inside this ocular fringe on the 

 dorsal surface is a little ridge of 8 to 10 minute conical spinelets 

 or papillfe, forming a semicircular collaret at the extreme tip. 



The actinal membrane is as transparent as the dorsal membrane, 

 the actino-lateral spinelets forming the floor of the test and pro- 

 jecting only their pointed tips beyond the sharp margin, to which 

 they impart a delicate serrate character. 



Colour, in alcohol, a light straw-colour, verging towards golden 

 brown. 



Station 122. Lat. 9° 5' S. to 9° 10' S. ; long. 34" 49' W. to 

 34° 53' W. Depth 350, 120, 32, and 400 fms. ; mud. (Unfor- 

 tunately only the station luimber is indicated on tlie label 

 accompanying these specimens ; and no record is given as to tlie 

 particular dredging in which they were obtained.) 



