420 FOUR-FOOTED AMERICANS 



Tamias — Ground Squirrels — Chipmunks 

 Smaller and lighter than the true squirrels, with the back 

 striped. 



Chipmunk Tamias striatus. 



Length of body, inches ; tail, 41 inches. 



Arctomys — Woodchucks 

 With heavy body, short ears and tail ; cheek pouches im- 

 perfect or none. Gnawing teeth very broad and strong. 



Woodchuck Arctomys monax. 



Length of body, 14J inches ; tail, 7 inches. 



Cynomys — Prairie Dogs 

 Intermediate in size between AVoodchucks and Spernio- 

 philes. Short ears; small cheek pouches; five clawed front 

 feet. Live in burrows in large communities and feed on 

 prairie grass. 



Prairie Dog Cynomys ludovicianus. 



Length of body, I^j inclies ; tail, 4 inches. 



Spermophilus — Spermophiles 

 Rather small and slender, tail variable. Ample cheek 

 pouches ; four front toes. Belong to prairies and dry, open 

 plains ; live in deep burrows and store up food for winter use. 

 Rock Spermophile .... Spermophilus grammurus. 



Length of body, 18 inches ; tall, inches. 



Striped Spermophile. . . . Spermophilus fridecemlineatus. 



Length of body, 7 inches ; tail, 44^ inches. 



Beaver Family 

 CastoridaB 



(Xiiniber of North American Species, One) 



Heavy skull; powerful teeth; strong front claws. Tail 

 flat and tongue-like. The best builder among Mammals. 



Beaver Castor canadensis. 



Length of bodv. 2 feet ; tail, 10 inches. 



