SHALLOW- WATER STARFISHES 51 



The most important generic feature is the fact that the genital 

 pores are on the actinal side, 1 between the proximal inferomarginal 

 plates, not dorsal, as in Asterias. The ovaries consist of compara- 

 tively few large digitate or glomerate tubules which, when filled 

 with the large ova, appear beaded. The genital ducts are short and 

 wide. 



Genus Evasterias Verrill, nov. 

 Type, E. troschelii (Stimpson). 



We may also distinguish this as a generic group, typified by 

 A. troschelii. In this the dorsal plates and ossicles are small and 

 reticulated, while there are three or more regular rows of stout inter- 

 actinal spines and plates. The increased number of rows of inter- 

 actinal plates and their closer union are the principal distinctions in 

 this case, but the number of plates varies with age, so that the young 

 specimens are essentially like Asterias in this respect. 



Genus Urasterias Verrill. 

 \ 



Plate LXX, figures 1-4. 



Type, U. linckii (Miiller and Troschel.) =A. stellionura Perrier. 



This type differs so much in structure from all others named that 

 it should probably be considered a distinct genus. 



The dorsal skeleton is very feebly developed, consisting mostly of 

 small plates and delicate, short, rod-like or linear ossicles, united in 

 an irregular network, with large meshes, but having a median 

 radial row of rather larger, slightly lobed, spiniferous plates, and 

 some similar lobed plates at the intersections of many of the meshes. 

 The dorsal spines are slender, irregularly scattered, except the 

 radials. Disk covered with a network of stouter, somewhat lobed 

 ossicles, bearing solitary spines, and usually having in the type a 

 larger flat plate, or group of such plates, at each interradial area, 

 above, and extending to the lower side, and usually perforated by a 

 pair of papular areas. This peculiar group of plates seems to be 

 made up of a considerable number of plates in the adult, often united 



1 This is true also of the genus Sporasterias of southern South America and 

 the Antarctic Ocean, including 5". antarctica (Lutk.), the type = Asterias 

 rugispina Stiinp. = A. spirabilis Bell = A. varia (Philippi) ; 5". rupicola Ver. ; 

 and several other nominal species; and probably, also, of A. studeri Per.; 

 Anasterias chirophora Lud. ; A. belgicce Lud. ; A. perrieri (Stud.) ; Podasterias 

 liitkeni (Per.) ; Stichaster nutrix (Stud.), which carry their young in the same 

 or a similar manner. They are all antarctic. 



