Tiidian Deep-sea Asteroidea. 81 



The infero-marginal plates correspond in number, size, and 

 shape with their exactly superposed fellows of the upper 

 marginal series ; they are uniformly covered with papilliform 

 granules, and, except in the apical third of the ray, each 

 bears near the middle of its distal (aboral) margin a long fine 

 accumbent spine, and often another, and occasionally two 

 other, similar but smaller spines vertically below the first. 



Adambulacral plates long and large, fairly coinciding base 

 to base with the infero-rnarginals, each with a straight 

 furrow-comb of 6 to 8 equal obtuse spinelets, and actinally 

 with a dense mass of smaller spinelets which usually fall into 

 three fairly distinct longitudinal series. Mouth-plates very 

 prominent, with widely open sutures, and with the most 

 central (adoral) furrow spine enormously enlarged ; actinally 

 each plate is thickly covered with spinelets in a triserial 

 arrangement. 



Actinal interradial areas narrow, but extending to the 

 eleventh or twelfth infero-marginal plate, and bearing thickly 

 spinulate plates, the spinelets of which have a tendency to 

 fall into pedicellaria-like clumps. 



Anus distinct, central, forming a longish chink-like vent to 

 a short broad intestine. Madreporiform plate placed near the 

 margin of the disk and much concealed by paxill^e. 



Colour in the fresh state uniform light rose-madder. 



Bay of Bengal, 1748 fathoms, Globigerina-oozo, and 

 pumice. 



The determination of the relations of this species has always 

 given me great trouble. Of described and figured bathybial 

 starfishes it comes nearest to Psilaster gracilis^ Sladen 

 (' Challenger ' Asteroidea, p. 230, pi. xli. figs. 5 and 6, 

 pi. xlii. figs. 9-11), which Mr. Sladen states to be so far 

 different from all its congeners that he only places it with 

 them with hesitation. As far as mere external characters go, 

 our species seems to agree with Psilaster gracilis in almost 

 every detail ; but I have satisfied myself by dissection that 

 our species has an alimentary canal with both ends opening 

 to the exterior, and for the present I leave it with 

 Dytast&r. 



PeesephonasteRj Alcock and Wood-Mason. 



Close akin to Plutonaster^ Sladen. 



Disk large, flat ; rays of moderate length, rigid. 



Marginal plates more or less covered with papilliform 

 spinelets and bearing each one Or many strong rigid spines : 

 tlic supero- marginals, which form a broad massive border on 



