56 VERRILL 



region. The genus Pisaster is here represented by seven or eight 

 large species, some of them being among the largest and most mas- 

 sive starfishes known. It is doubtful if the restricted genus occurs in 

 any other fauna. The genus Orthasterias, with seven or eight 

 species, is uncommon elsewhere. Its nearest allies are Atlantic 

 species and Distolasterias of Japan. 



A large proportion (fifteen) of the species of this region are 

 normally six-rayed, which is a remarkable peculiarity. 



Over twenty nominal species of Asteriinae had been already de- 

 scribed from the Northwest Coast, between southern California and 

 the Arctic Ocean. In the collections studied by me there are about 

 thirty additional species, besides twenty well-marked new varietal 

 forms, or a total of about seventy. 



Probably no other fauna is so rich in species of this group. 1 It 

 is not improbable, however, that some of the supposed species may 

 prove to be only local varieties, when larger series can be carefully 

 studied. This may possibly prove true of some of the larger forms 

 described by Stimpson, allied to Pisaster ochraceus and P. capitatus, 

 but on the other hand there are probably many additional species to 

 be found by dredging in moderate depths. Nearly all the known 

 species of this region are littoral or very shallow-water forms. 

 Deep-water species are not described in this report. 



I. ANALYTICAL TABLE OF THE GENERA, SUBGENERA, SPECIES, 

 SUBSPECIES AND VARIETIES OF ASTERIIDJE FROM THE 

 NORTHWEST COAST OF AMERICA. 



1. Dorsal skeleton continuous, formed mostly of lobed plates and smaller 



ossicles overlapping at the ends; dorsal plates not isolated. Rays 

 five or six, rarely more, unless autotomous. 



2. Adambulacral spines all attached to the actinal face of the plates; none 



attached higher within the grooves. 



3. Adambulacral spines in a single regular row, one to a plate, in the adult 



(monacanthid). 



A. Interactinal plates present, at least in adults, and usually bearing spines. 



C. Disk thick, rather large ; rays five or six, stout, thick at base. Dorsal os- 

 sicles strong, numerous, not confined to three or five rows. Dorsal 

 skeleton reticulate or irregular. Dorsal and lateral dermal major 

 pedicellariae sessile, large, stout, erect, ovoid or wedge-shaped, often 

 nearly as thick as the spines, and usually strongly denticulated at 

 the tips of the valves (unguiculate). 

 Genus Pisaster M. and Tr., p. 67. Type, P. ochraceus (Br.). 



*The only other region that can be compared with this in the number and 

 variety of Asteriinae is the southern coast of South America, especially around 

 Tierra del Fuego and Patagonia, whence numerous genera and species have 

 been described, mostly very unlike the northern forms. (See below, p. 351.) 



