JAPANESE ASTEROIDEA. 



209 



the anns and certain differences in the arrangement of the 

 adambnlacral spines, though closely similar to that genus in other 

 respects. The superambulacral plates are very well developed, and 

 the whole external characters appear to me amply sufficient for 

 placing this species in the genus Persephonaster as defined by 

 Alcock. 



The colour of the alcoholic specimens is light straw yellow ; 

 the measurements are as follows : 



The characteristic points in the general features of this species 

 are the generally fragile character of the spines, the comparatively 

 ample spaces left between the paxillas, even in the subcentral area 

 of small paxillas around the anus, the comparative largeness of 

 the disk, and the presence of a very slender terminal portion in 

 each arm, where the superomarginals of the two sides are separated 

 from each other only by about two rows of paxilla?, the arms 

 undergoing at this point a comparatively sudden constriction from 

 side to side (PI. II, fig. 23). 



Superomarginals.— llhQ number of superomarginals is given in 

 the foregoing table. At the middle of the arm they are nearly 

 twice as broad as high, but at the interradial angles they are 

 twice as high as broad, and their breadth gradually increases 

 from the interradial angle to about the middle of the arm and 

 then gradually decreases again towards the distal portion of the 

 arm. 



