144 RODENTS OP IOWA 



Genus Tamias Illiger. 



Back conspicuously striped ; tail short, not bushy ; cheek pouches 

 large; postorbital processes slender, pointed, directed obliquely 

 backward and downward ; infraorbital foramen oval, confined to 

 lower part of maxilla. 



Be)ital formula— I, 1/1 ; Pm. 1/1. M. 3/3=20. 



Key to Species of Tamias. 



Back with two whitish stripes, and five black ones; chestnut 

 rufous on rump ; total length, about 9.60 inches. 



Chipmunk. 

 Tamias striatus strkitus, p. 2fi 



Similar to above, but grayer and larger ; rump einnamon brown ; 

 total length, al)out 10.25 inches. 



Gray Chipmunk. 

 Tamias striatus griseus. p. 27 



Subfamily MARMOTIN/E. 



Genus Citellus Oken. 



Body rather slender ; tail variable in leng-th, but not bushy ; 

 ears variable, but not tufted ; cheek pouches large ; front feet 

 with four well developed toes, the thumb rudimentary; hind feet 

 with five toes ; postorbital processes slender and spinelike ; ante- 

 orbital foramen circular, a tubercle on lower outer edge ; two 

 upper premolars, the first much smaller than the second. 



Dental formula— 1. 1/1; Pm. 2/1; M. 3/3=22. 



Key to Species of Citellus. 



Color grayish brown, not striped ; total length, about 15.00 

 inches. 



Franklin's Spermophile. 



Citellus franklini. p. 36 



Back with seven yellowish white lines, which alternate with 

 six rows of rounded, yellowish white spots in a brown background; 

 total leng-th, 10.50 inches. 



Thirteen-lined Spermophile. 

 Citellus tridecemlineatus tridecemlineatus. p. 29 



