A NEW GENUS OF SEA STARS — FISHER 455 



The adambulacial, actinal, and the lateral abactmal plates of Para- 

 sterina crassa are in no way different from those of Nepanthia. This 

 leaves only the enlarged plates of the median abactinal area with the 

 numerous intervening secondary plates and superficial tertiary plates 

 upon which to base a new genus. But Parasterina occidentalis Clark 

 (1938, p. 180, pi. 21, fig. 5) has no secondary abactinals. It is ques- 

 tionable, therefore, whether we can place too much reliance for generic 

 characters upon these median abactinal plates. The behavior of the 

 abactinal plates of Nardoa furnishes reason for caution. In N. pauci- 

 foris the plates are numerous, small, and most nearly uniform in size. 

 Somewhat larger and progressively more diverse as to size are those 

 of A'', mollis, N. tuberculata, and N. novaecaledoniae, while in N. tumu- 

 losa and A^. frianti the large primary plates are hemispherical and the 

 secondaries small and much more numerous (Fisher, 1919, pis. 108- 

 110). The possibility must be considered that in Nepanthia species 

 exist with overdeveloped primary abactinal plates. They are not a 

 rare occurrence in the Asteroidea, and in certain species of the As- 

 teriidae (e. g. Leptasterias polaris, Pisaster ochraceus) are of less than 

 specific value. Both Parasterina crassa (Gray) and P. occidentalis 

 Clark must be regarded with suspicion. I think the former is an aber- 

 rant Nepanthia, and that Parasterina should consequently be discarded. 



