ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 53 



ginals remains tlie most conspicuoiis difference. By tlie same reasoning it is inij)()s- 

 sible to separate generically anomahta from pacijicus. In the former the width of 

 the superomarginals has been found to vary considerably; hence if this character 

 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. anomalus rej)resent two extremes, with pacijicus in between. 

 L. proplnquus, described below, somewhat resembles L. l-erguelenensis when viewed 

 from above, and still more Mimastrr cognatus, although the interbrachial arcs are 

 rounder and the infcromarginals wider in proportion to length. As noted under 

 Gephyreaster smfti, in view of the range of variation within the genus Le.ptycliasUr, 

 it is very doubtful if Mimafiter cogrmtus is a Mimaster. It seems to be a Lepty- 

 chaster. 



LeptycJMster anomalus bears a striking resemblance to Parastropecten inermis 

 Luihvig, which appears to be basetl on young specimens, however. From this 

 species anomalus differs in having three or four furrow spinelets instead of six or 

 seven, in having five or six papulae about each plate or paxilla instead of four, 

 and in having a minute anal opening. 



The diagnosis given by Ludmg for Parastropecten is as follows:" Die neue 

 Gattung unterscheidet sich von Astropecten tlurch den volligen ilangel von unteren 

 und oberen Randstacheln, durch kurze Arme und durch verhaltnismassig grosse 

 ventrale Interradialfelder, deren Flatten ( = VentrolateralpIatteu) eine paxilliire 

 Form haben. In other words, the genus is erected on the strength of the unarmed 

 marginals and large actinal areas — just the features in which Leptychaster differs 

 from Astropecten, for the size of the superomarginals has been sho\vn to be variable 

 witliin a species, and not diagnostic of the genus. 



The impossibility of recognizing a separate genus Parastropecten for inermis 

 and anomalus is the fact that Leptychaster propinquus would have to be ranked 

 under Leptycliaster on account of the small superomarginals, L. anomalus, of course, 

 untler Parastropecten, L. pacificus probably under Parastropecten, on account of 

 the larger superomarginals, although it is obviously a close relative of L. arcticus. 

 To divide the genera on the presence or absence of an anus would lead to the 

 ranking of Parastropecten inermis and Leptychaster arcticus under one genus antl 

 the other forms under another, and would necessitate ignoring the very characters 

 upon wliich we base genera. 



Consequently, although Parastropecten seemeti fully warranted when described, 

 it seems best now to merge it with Leptycliaster. 



The genus Glyphaster Vcrrill based (without diagnosis) on L. anomalus seems 

 to be synonymous with Parastropecten, which would therefore have precedence if 

 anomalus constituted a separate genus. Since there arc intergrailing forms with 

 arcticus, I have no hesitation in saying that neither Glyphaster nor Parastropecten 

 can be so diagnosed as to include Leptychaster propinquus and exclude typical 

 Leptycliaster. 



I have examined two small specimens from the Sea of Japan, collecteil bv the 

 Albatross in 1906. If the tiny specimen from off Monterey is certainly anomalus, 



a Mem. Mua. Comp. Zool., vol. 32, 1905, p. 76. 



