HAPLODONTIA. 



Lower jaw massive; angle of niandiblo rounded. Incisors large, 

 powerful, the lower much longer than the \ipper, with chisel-like 

 edges, and deep orange-red color exteriorly. 



■lli. Castor. 



Castor, Linn. Syst. Nat., 1766, p. 78. Type. C. fiber, Linn. 



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 to quite late in life. 



Fig. 27. Castor canadensis. 



No. 88 Field Columbian Museum Coll. ■< Nat. 



