1916] 



Taylor: Beavers of Western North America 



431 



Fig. G. Outline of posterior portion of cranium 

 of beaver, to illustrate method of 

 measuring dorsal outline foramen 

 magnum to inion, or most dorsal point 

 on outline of foramen magnum to 

 occipital crest on median line. About 

 one-half natural size. 



Belugae, on the basis of the table of measurements, has longer 

 antero-posterior diameter of P 4 than in leucodonta, although speci- 

 mens nos. 4347 from Cook Inlet and 12101 from Vancouver Island 

 are nearly the same in this respect, (see table IV, p. 428). Belugae 

 generally has broader teeth transversely than in leucodonta (P 4 in 

 specimen no. 12101, from Vancouver Island exceeds P 4 in no. 4347, 

 from Cook Inlet). 



Fig. H. Outline drawings of tails of different races of western beavers. 

 Approximately one-sixth natural size. 

 a. Castor subdural n s subauratus, 9, no. 12654, Mus. Vert. Zool.; Gray- 

 son, San Joaquin River, Stanislaus County, California. 

 6. Castor canadensis leucodonta, 9, no. 12107, Mus. Vert. Zool.; 

 Alberni, Vancouver Island, British Columbia. 



c. Castor canadensis pliaeus; solid line, no. 210, Mus. Vert. Zool., 9, 



Hasselborg Lake, Admiralty Island, Alaska; dotted line, no. 209, 

 Mus. Vert. Zool., $ , Pleasant Bay, Admiralty Island, Alaska. 



d. Castor canadensis frondator, 9, no. 20751, U. S. Nat. Mus.; San 



Pedro River, Sonora, Mexico. 



e. Castor canadensis canadensis; inner line, no. 174526 9 , U. S. Nat. 



Mus., Nepisiquit River, New Brunswick; outer line, no. 174525 $, 

 U. S. Nat. Mus., same locality. 



