430 University of California Publications in Zoology [Vol. 12 



Mus. Vert. Zool.) is at hand. For comparison of this with Castor 

 canadensis leucodonta see below. A comparison with Castor cana- 

 densis canadensis is given in table opposite p. 432. 



Range. — It is impossible at this time to define precisely the limits 

 of range of Castor canadensis bclugac. Specimens from the follow- 

 ing localities have been examined : Beluga 

 River (tributary to Cook Inlet from the 

 north) ; Nenilchuk (sometimes spelled Ninil- 



_,. „ „ „. „ . chik [Baker, 1906, p. 4631, a village on east- 

 Fig. F. Outline ot ham- 



ular process, show- era shore of Cook Inlet, south of the mouth 



ing method of taking f the Kasilof River) ; Kasiliff (probably 



measurement. About _ . 



one-half natural size Kasiloi, a fishing village at the mouth ot 



Kasilof River, Cook Inlet, according to 

 Baker, 1906, p. 353) ; Snug Harbor, Alaska Peninsula (probably 

 Snug Harbor on the western shore of Cook Inlet, near Iliamna Peak 

 [Baker, 1906, p. 586]); and the general vicinity of Stuart Lake, 

 British Columbia. 



It is probable that the form occupies territory on the mainland 

 from central British Columbia on the south to the Alaskan Moun- 

 tains on the north. The main chain of the Rocky Mountains doubt- 

 less bounds its range on the east, and the ocean, or possibly certain 

 coast mountains on the west. 



This region is much interrupted topographically and it is not 

 unlikely that adequate material would show considerable local differ- 

 entiation, possibly the presence of well-marked subspecies, within its 

 boundaries. Militating against this suggestion, however, is the 

 observed similarity of specimens from such widely separated points 

 as the Cook Inlet region, Alaska, and Stuart Lake, British Columbia. 



Remarks 

 Comparison With Castor canadensis leucodonta Gray 

 The new subspecies, belugae, is perhaps nearest leucodonta, of 

 which examples from Vancouver Island are at hand, although it is 

 intermediate between that form and canadensis from eastern Canada. 

 Crania can be distinguished from leucodonta by the narrower blades 

 of the hamular processes of the pterygoids in belugae (see fig. F, 

 above) ; by the ridge laterally on the rostrum less strongly developed 

 than in leucodonta; by the tendency in belugae for maxillary tooth- 

 row to be longer, shown also in ratio of maxillary tooth-row to basilar 

 length. 



