GEOMYID^E. XII. 39 



FAMILY XL CASTORIDJ3. 



( The Beavers.) 



Aquatic Rodents of large size, having the molars 

 rootless, :f-, or J;J; fore feet with five distinct toes and 

 claws; tibia and fibula distinct; no postorbital process. 

 A small family, containing but two existing genera, 

 Anisonyx of our N.W. coast, and Castor. 



* Molars 4r4 above ; hind feet webbed ; tail broad, flat, and scaly. 



CASTOR, 1. 

 /. CASTOR, Linnaeus. BEAVERS. 



1. C. fiber, L. BEAVER. Mexico to the Polar Sea; 

 now being rapidly exterminated. (C. canadensis^ Kuhl.) 



FAMILY XII. GEOMYHLE. 



(The Pouched Gophers.) 



Cheek pouches large and distinct, opening outside of 

 the mouth. Molars J:f; incisors large and thick; skull 

 heavy; temporal bones enormously developed. Limbs 

 about equal, the fore claws, five in number, very large; 

 tibia and fibula united. Body thick-set and clumsy. 



Genera two, Geomys and Thomomys, all North Ameri 

 can, and chiefly inhabiting the central plains; habits 

 nocturnal and subterranean. 



* A large groove near the middle of each upper incisor ; crown 



of molars elliptical GEOMYS, 1. 



/. GEOMYS, Rafinesque. POUCHED GOPHERS. 

 1. G. bursarius, (Shaw) Rich. POCKET GOPHER. Red 

 dish brown, with plumbeous tinge. Prairies, Wis. and 

 Ills., westward. 



FAMILY XIII. ZAPODHLE. 



(The Jumping Mice) 



Hind legs greatly elongated, adapted for. taking long 

 leaps; fore legs short. Tail very long. Molars -f:-f-; 



