CASTOR. 159 



now become extinct in the majority of localities. Its skin and scent 

 bags were too valuable commercially to preserve it from man's 

 rapacity. It is probably one of the best -known rodents in the land, 

 and most persons have some knowledge of the beaver's house and 

 dam, or have seen the trunks of trees that have been cut down by 

 the wonderful adze-like incisors. Clothed in a dense furry coat im- 

 pervious to water, and provided with paddle-like hind feet and a broad 

 rudder-like tail, the beaver is at home in the lake or river, where 

 most of its life is passed. It shuns the vicinity of man, and exists 

 only in the virgin wilderness. 



Fam. II. Castoriche. Beavers. 



Skull massive, no postorbital processes, superior outline nearly 

 straight; molars single-rooted, with re-entering of enamel folds, and 

 decreasing in size posteriorly; the molar series is not parallel but con- 

 verges anteriorly, and the palate is arched, contracted anteriorly. 

 Incisors large, powerful, the lower much longer than the upper, with 

 chisel-like edges, and a deep orange red color exteriorly. Lower jaw 

 massive; angle of mandible rounded. 



39. Castor. Beaver. 



Tim- P!=I- M^= 20 



1 -i-i' r 'l I' 1Yi '3-3 



Castor Linn., Syst. Nat., i, 1758, p. 58; i, 1766, p. 78. Type Castor 

 fiber Linnaeus. 



Feet four-toed, hind feet large, webbed; upper molars subequal, 

 with one inner and two outer enamel folds; tail broad, flat, scaly; 

 molars with dentinal pulp persisting until quite late in life. 



canadcnsis frondator (Castor), Mearns, Proc. . U. S. Nat. Mus., 



1897, P- 5 02 - Elliot, Syn. N. Am. Mamm., 1901, p. 116. 

 SONORAN BEAVER. 



Type locality. San Pedro River, State of Sonora, Mexico, near 

 monument No. 98, Mexican boundary. 



Geogr. Distr. From State of Sonora, Mexico, to Wyoming and 

 Montana. 



Gcnl. Char. Size large; scaly portion of tail less than twice as 

 long as wide. 



Color. Upper parts russet, chocolate at root of tail; under parts 

 grayish cinnamon to ferrugineous beneath tail; sides wood brown 

 varied with tawny olive; feet burnt sienna. 



