438 



University of California Publications in Zoology [Vol.12 



IX. Measurements and Ratios of Scaled Portions of Tails 



Museum 



Subspecies — number 



Castor c. phaeus 209 



Castor c. phaeus 210 



Castor c. canadensis 174526 



Castor c. canadensis 174525 



Castor c. canadensis 4358 



General cranial characters. — (See table of measurements, oppo- 

 site.) Crania compared : Castor canadensis phaeus, nos. 209 £ , and 

 210 3, Mus. Vert. Zool., from Admiralty Island; and Castor cana- 

 densis canadensis, nos. 174525 $ , 174526 2 , U. S. Nat. Mus., from 

 New Brunswick. 



Interorbital constriction decidedly narrower in phaeus. Nasals 

 in phaeus longer and narrower. Foramen magnum broader, the 

 difference amounting to 13 and nearly 15 percent respectively in 

 nos. 210 and 209, percentage taken on the basis of the average 

 width in canadensis. Maxillary tooth-row longer in phaeus, conse- 

 quently ratio of this measurement to basilar length greater. Teeth 

 in phaeus with a tendency to be longer than in comparable skulls 

 of canadensis. 



Process in middle of interpterygoid fossa shorter in phaeus. 

 Hamular processes of pterygoid (see fig. F, p. 430) broader-bladed in 

 phaeus (no. 209, 4.1 mm.; 210, 4.1; no. 174525, 3.5; 174526, 3.1). 



Chief points of difference: Narrower interorbital constriction 

 (in phaeus), nasals of different length and outline, broader foramen 

 magnum, longer maxillary tooth-row, longer teeth. 



Comparison With Castor canadensis belugae Taylor, from the Cook Islet 

 Region 



General external characters. — Specimens compared: Castor can- 

 adensis phaeus, nos. 128 $ , 129 $ , 185 <? , 209 S , 210 <? , and 211 $ , 

 Mus. Vert. Zool., from three localities on Admiralty Island, Alaska ; 

 Castor canadensis belugae, no. 4347 $ , Mus. Vert. Zool., Snug Har- 

 bor, Alaska Peninsula. The specimens of phaeus were collected, as 

 above stated, between May 16 and June 1. The single skin of 

 bdugae was secured June 14, 1904. 



