1916] Taylor: Beavers of Western North America 455 



Comparison With Castor canadensis leucodonta Gray, from Vancouver 

 Island, Castor canadensis pacificus Rhoads, from Washington State, 

 Castor canadensis canadensis Kuhl, from Eastern Canada, and Castor 

 canadensis belugae Taylor, from Cook Inlet Region, Alaska 



General external characters 

 Specimens compared. — Castor canadensis frondator, no. 20751 9 , 

 U. S. Nat. Mus., from San Pedro River, Sonora, Mexico, October 14, 

 1892; Castor c. leucodonta, nos. 12101-12111, Mus. Vert, Zool., all but 

 the last (which is from Great Central Lake) from Alberni, Vancouver 

 Island, British Columbia, June 11 to August 25, 1910; Castor c. 

 canadensis, no. 4358 $ , U. S. Nat. Mus., Moose River, Ontario, Hud- 

 son Bay region, May 21, 1860 ; and nos. 174525 $ , 174526 2 , both 

 U. S. Nat. Mus., Nepisiquit River, New Brunswick, September 25, 

 1911; Castor c. belugae, no. 4347 $ , Mus. Vert. Zool., Snug Harbor, 

 Alaska Peninsula, Cook Inlet region, June 14, 1904. 



Since leucodonta is, in general, close to pacificus, and since no 

 material of pacificus representative of external characters and com- 

 parable with frondator is available, comparison has been made between 

 frondator and leucodonta. 



XXI. Measurements and Ratios of Scaled Portions of Tails 



All measurements in millimeters, and taken in dry skins; see fig. H, p. 431 



Ratio 



Museum width to 



Subspecies — number Length Width length 



Castor c. frondator 20751 232 113 48.9 



Castor c. leucodonta 12101 237 120 51.0 



Castor c. leucodonta 12111 243 108 44.6 



Castor c. leucodonta 12107 270 124 46.0 



Castor c. canadensis 174525 265 116 43.4 



Castor c. canadensis 174526 260 108 41.3 



Castor c. canadensis 4358 223 92 41.1 



Castor c. belugae 4347 245 115 47.0 



In general, the pelage is not so heavy-weighted, either in frondator 

 or in leucodonta as in canadensis. General coloration in canadensis 

 dark; in leucodonta paler; in frondator lightest. Frondator has the 

 most uniform coloration. The overhair laterally is, however, of a 

 brighter tint than that mid-dorsally, the lightest area being the 

 cheeks. The single skin of belugae is darker than frondator, but 

 paler than the New Brunswick canadensis. In proportions of tail it 

 is closer to frondator than are the examples of canadensis. Propor- 

 tions of scaled portion of tail are not clearly separative as regards 



