SHALLOW-WATER STARFISHES 45 



these are not yet known from the northwestern coast, but are likely 

 to occur hereafter, when more dredging shall have been done, and 

 therefore it may be useful to give here a summary account of the 

 principal groups of this kind. 



Genus Coscinasterias Verrill. 



Coscinasterias VERRILL, Trans. Conn. Acad. Sci., i, p. 248, 1867. (Type, C. 



muricata V. = (?) C. calamaria (Lam.).) 

 Stolasterias (pars) SLADEN, Voyage Chall., vol. xxx, pp. 563, 583, 1889. (Type, 



C. tenuispina.) Non Perrier. 

 Coscinasterias and Polyasterias PERKIER, Exped. Trav. et Talisman, p. 108, 



1894. 



Body small, rays elongated, somewhat angular, usually carinate. 

 Dorsal ossicles of the rays stout, four-lobed, usually arranged in 

 three or five regular rows, besides the upper marginals, which form 

 regular lateral rows. Actinal ossicles usually consist of one primary 

 (peractinal) row, like the lower marginals, but they may be rudi- 

 mentary and spineless in half-grown specimens, and only bear spines 

 in large, mature individuals, as in C. tenuispina. 



Minor pedicellarise are abundant. Large forficulate or major pedi- 

 cellariae of the usual forms are present, often in considerable num- 

 bers, on the dorsal and lateral plates, and smaller ones occur on 

 the marginal areas. Large unguiculate pedicellariae are lacking. 

 Adambulacral plates monacanthid or nearly so. Often autotomous; 

 rays variable in number. Madreporites often two or more. 



Stolasterias, which was proposed as a subgenus by Sladen in 1889, 

 was nearly identical with Coscinasterias, characterized by me in 1867. 

 He gave no reason for changing the name. It should be regarded as 

 a synonym of the latter and be eliminated. Sladen's type was 

 A. tenuispina, which is a Coscinasterias with the peractinal plates 

 rudimentary and without spines, except in the larger specimens. 



M. Perrier ( 1894) correctly retained Coscinasterias for the typical 

 forms, like calamaria, but separated those species that are known to 

 undergo spontaneous fission under the name of Polyasterias = 

 typical Stolasterias Sla., though they do not appear to differ much 

 in structure from the preceding, while he retained Stolasterias Sla., 

 in a restricted sense, for those allied to glacialis t although C. tenui- 

 spina was named by Sladen as the type. 



As C. tenuispina often divides spontaneously, it belongs to Poly- 

 asterias in Perrier's arrangement. This would make the latter 

 strictly synonymous with Sladen's typical Stolasterias, which should 



