FIELD BOOK OF MAMMALS 



Genus Castor 



Dentition: Incisors, {; Canines, §; Premolars, }; Molars, f = 20. 



Beaver. — Castor canadensis 



and related forms 



Names. — Beaver; American Beaver. Plate XXVII. 



General Description. — Size very large, largest of North 

 American rodents; form robust; tail broad, flat, scaly; ears 

 short; five toes on fore and hind feet; hind feet webbed, with 



Fig. 65. Beaver 



claw of second toe double or cleft ; anal glands present ; pelage 

 composed of long, hard hairs and soft short underfur; color 

 brown; habit aquatic. 



Color. — Sexes colored alike ; no very great seasonal variation. 



Upperparts rich dark brown, the long hairs chestnut-brown, 

 •:he underfur without any reddish tinge ; head brighter ; incisors 

 orange; underparts somewhat lighter in tone than upperparts 

 and lacking the chestnut tinge. 



Immature pelage. — Practically as in adults, perhaps a little 

 lighter in general tone. 



In worn or summer pelage the long hard hairs may be 

 so scanty that the pelage seems to be made up of the duller 

 and browner underfur. 



328 



