54 VERRILL 



Genus Meyenaster Verrill. 

 Type, M. gelatinosus (Meyen, 1834). Chile. 

 Meyenaster Verrill, op. cit., 1913, p. 485. 



Adambulacral plates monacanthid; one row of larger interactinal 

 spines on thick ovate plates, each in line with two similar spines on 

 each inferomarginal plate; superomarginal plates stout, each alter- 

 nate one with a single large spine ; a wide intermarginal lane bearing 

 a regular row of papular areas, twice as many as superomarginal 

 spines, and many large pedicellarise. A row of median radial stout 

 spines, usually one on each alternate plate ; in large specimens an 

 intermediate imperfect row on each side; media-lateral skeleton 

 reticulated irregularly with numerous short, transverse and oblique 

 ossicles defining five or six irregular series of large papular areas 

 on each side. Central part of disk symmetrically stellate with a 

 central and twelve surrounding spines, in type. Large, stout pedi- 

 cellarias dorsal, lateral, and intra-ambulacral, compressed, ovate-tri- 

 angular, not unguiculate; many very small acute, major pedicellariae 

 on papular areas ; minor pedicellarise abundant on large, broad, fleshy 

 circumspinal sheaths. A thick, strongly canaliculated skin covers and 

 conceals all the plates. 



G. ANALYTICAL TABLE OF THE GENERIC AND SUBGENERIC 

 GROUPS OF NORTHERN ASTERIIN^ HAVING RETICULATED 

 DORSAL SKELETONS. 



A. Monacanthid. Dorsal skeleton coarsely reticulate. Interactinal spines 



and ossicles well developed, in several rows. Large unguiculate 

 erect pedicellariae are present ; rays five or six. 

 Pisaster (Ag.). Type, P. ockraceus (Brandt). 

 AA. Usually diplacanthid, or alternately diplacanthid and monacanthid, rarely 

 triplacanthid. Interactinal plates and spines present or absent, or 

 rudimentary. 



B. Adambulacral spines confined to the outer or actinal surface of the plate. 



C. Dorsal plates mostly angular or lobed. Interactinal plates and spines 



forming at least one row (peractinal), usually with other shorter 

 proximal rows. Both rows of marginals well developed. 

 Asterias, sens ext. 



D. Dorsolateral plates and transverse ossicles openly reticulated. 



a. Interactinal plates strong, closely united, or imbricated in three or more 

 rows in the adult, bearing several regular close rows of nearly 

 uniform spines, like the inferomarginals ; intervening papular areas 

 small. Two kinds of major pedicellarise usually present. Dorsal 

 spines unequal, several on a plate, reticulate or areolate. 

 Genus Evasterias V. Type, E. troschelii (St.). 



