A NEW SEA STAR OF THE GENUS EVASTERIAS 



By W. K. Fisher, 

 of the Hopkins Marine Station, Pacific Grove, California 



Species of the genus Evasterias are confined to the intertidal zone 

 and shallow water of the North Pacific, from the Okhotsk Sea to 

 central California. The center of abundance is the region betv^'een 

 southern Alaska and Puget Sound. 



The genus diifers from Asterias in having numerous actinai plates 

 (each having one or two spines) arranged in from three to six 

 longiseries, which alternate with longiseries of large uctinal papulae ; 

 inferomarginal plates lateral rather than actinai in position.^ 



There are two very distinct species, Evasterias troschelii Stimpson 

 and E. echinosoma^ herein described. Evasterias troschelii is one of 

 the most variable of sea stars, which is admitting a good deal. Study 

 of a large number of specimens indicates the existence of three fairly 

 distinct, intergrading formae each with numerous variations. 



1. Forma troschelii, the type form, with very unequal abactinal 

 spines not arranged in a well-defined reticulum. This includes 

 Asterias victoiiana Verrill, Leptasterias macouni Verrill (a six- 

 rayed young), Evasterias troschelii, var. rudis Verrill, a fully grown 

 or giant specimen. (Pribilof Islands to Puget Sound.) 



2. Forma dlveolata Verrill, very variable, but in general with 

 coarse spines arranged in a reticulate pattern. This form is Stimp- 

 son's interpretation of Brandt's Asterias epichlora, a name applied 

 by Verrill (1914) to a small, six-rayed Leptasterias of the Alaskan 

 coast. I think that Stimpson was correct and that Verrill is mis- 

 taken. Brandt's type was five-rayed, not six ; the form is sometimes 

 green above, as the name implies. This form includes Asterias 

 hrachiata Perrier, 1875 (preoccupied) ; Evasterias troschelii, var. 

 alveolata Verrill, var. parvispina Verrill, and the " typical form " 

 cited and figured by Verrill in 1914.^ (Unalaska to Carmel Bay, 

 Calif.) 



1 Fisher, a Preliminary Synopsis of the Asterildae, Ann. and Mag. Nat. Hist., spr. f>, 

 vol. 12, 1923, p. 590. 



* Shallow-water Starfishes of the North Pacific Coast, etc. Harrinian Alaska series, 

 vol. 14, p. 153, pi. 26, figs. 1 and 2. 



No. 2632.— Proceedings U. S. National Museum, Vol. 69. Art. 6 



2996—26 



