1916] Taylor: Beavers of Western North America 443 



hand. Nearest in these respects are iios. 12103, 12104, from Hall's 

 Ranch, Alberni Valley, Vancouver Island, taken June 15 and 18, 

 respectively, 1910. As regards change in external characters with 

 age, it should be called to mind that the modifications arc not 

 great in the material worked over (see p. 420). Respecting seasonal 

 change our knowledge is less complete. 



In Castor c. leucodonta the dorsal overhair appears darker than 

 in Castor c. pacificus (see table XII, opposite p. 440, for comparison 

 of characters). The general coloration belongs to the cinnamon series 

 in both. The darker impression doubtless is the result of the presence 

 in leucodonta of more dark hairs sprinkled in with the light, as, for 

 example, in no. 12108. In leucodonta the dorsal underfill' is a darker 

 shade of brown than it is in pacificus. 



Ventral coloration shows the same general relation, having a 

 darker cast in leucodonta than in pacificus. The overhair ventrally 

 is in leucodonta about as much darker than it is in pacificus as 

 benzo brown is darker than cinnamon-drab. No color difference as 

 regards underfur ventrally could be distinguished. The difference 

 in coloration extends to the feet. The hind feet are hazel to carob 

 brown in leucodonta, while in pacificus they are close to benzo 

 brown. 



General cranial characters. — Nasals in Castor c. leucodonta give 

 the impression of being longer and narrower than in pacificus, 

 though the measurements show the reverse to be true in the matter 

 of length. Nasals in pacificus have their outlines somewhat more 

 invaded laterally by the backward-extending tongues of the pre- 

 maxillaries. This lateral invasion of the nasal outline occurs at a 

 point farther anteriorly in pacificus than it does in either leucodonta 

 or belugae. Beginning at the anterior end of the skull, and pro- 

 ceeding posteriorly, the nasal outlines are at first nearly parallel, 

 then the premaxillaries interrupt the outline, and the nasals become 

 somewhat narrowed, their lateral outlines again attaining a nearly 

 parallel relation. This posterior parallel portion of the outline is 

 longer in pacificus than in leucodonta, Looking at the crania in 

 their anterior aspect there is manifest a tendency for the nasals to 

 fall away in a regular curve from the median line. In leucodonta, 

 on the other hand, the usual condition is a flatfish area dorsally on 

 the median line. In the mainland examples the nasals extend far- 

 ther down on the side of the rostrum anteriorly, showing a condi- 

 tion which may be described as a droop. The nasals as a rule do 



