Order RODENTIA 



8. 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 



9. 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 ; b, portion of skull of 

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

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

 side {f, incisive foramen) ; e, skull of woodchuck, top view. 



