128 



Order RODENTIA 



Upper jaw with 5 cheek teeth on each side; anteriormost 

 tooth rudimentary, eastern gray squirrel, Sciurus carolinensis 



Upper jaw with 4 cheek teeth on each side 



eastern fox squirrel, Sciurus niger 



Upper incisors each with 2 longitudinal grooves, fig. 73c. 

 plains pocket gopher, Geomys bursarius 



Upper incisors each with 1 or no groove 10 



Fig. 73. — Characters used in the identification of rodents: a, skull 

 of thirteen-lined ground squirrel, top view ; />, portion of skull of 

 Franklin's ground squirrel, top view (/>, postorbital process) ; c, 

 front of rostrum of pocket gopher; d, rostrum of beaver, under 

 side (/, incisive foramen) ; e, skull of woodchuck, top view. 



