JAPANESE ASTEROIDEA. 249 



" BemarJcs. — The reasons which may be advanced for placing this species 

 tinder the genus LeptycJmster are the following : Lepty chaster arcticus, which 

 ranges into Bering Sea, has in the same region a close relative, pacificus, 

 wliich differs in possessing broader and less numerous marginal plates. The 

 superomarginals of arcticus are tln"ougliout the ray scarcely larger than 

 paxillfe, but are of conspicuous size in pacificus, and in the interbrachial 

 region are considerably wider than midway along ray. After a close com- 

 parison of the two forms it has not been possible to separate them gene- 

 rically. The character of the marginals, abactinal paxillae, adambulacral 

 plates and armature, distribution of gonads, and distribution of papulae are 

 essentially the same in the two forms. The width of the sux^eromargiuals 

 remains the most conspicuous difference. By the same reasoning it is 

 impossible to separate generically cmomalus from pacificus. In the former 

 the width of the superomarginals has been found to vary considerably ; 

 hence if this cliaracter is unstable for a species it obviously can not be 

 used to diagnose a genus. The wholly unarmed marginals remain, however, 

 very characteristic of the genus. Thus L. arcticus and L. cmomalus re- 

 present two extremes, with pacificus in between. L. propinquus, described 

 beloAv, somewhat resembles L. Icerguelensis when viewed from above, and 

 still more 3Iimaster cognattis, although the interbracliial arcs are rounder and 

 the inferomarginals wider in proportion to leng-th. As noted under GepJiy- 

 reaster siuifti, in view of the range of variation within the genus Lepty cliaster, 

 it is very doubtful if Mimaster cognatus is a Mimaster. It seems to be a 

 Lepty chaster. 



" Leptychaster anomcdus bears a striking resemblance to Parastropecten 

 inermis Ludwig, which appears to be based on young specimens, however. 

 From tliis species anomcdus differs in having three or four fun'ow spinelets 

 instead of six or seven, in having five or six papulœ about each plate or 

 paxilla instead of four, and in having a minute anal opening. 



"The diagnosis given bj' Ludwig for Parastropecten is as follows 

 [ : 05, p. 76] : * Die neue Gattimg imterscheidet sich von Astropecten dm'ch 

 den völligen Mangel von imteren und oberen Eandstacheln, durch km'ze 

 Ai-me imd dm'ch verhältnismässig grosse ventrale InteiTadialfelder, deren 



