140 CITELLUS. 
Body rather slender; tail either long, moderate, or short, varying 
greatly in its length among the different species; ears large to rudi- 
mentary, not tufted; cheek pouches large; skull variable, short and 
broad like Sciurus, or long and narrow; postorbital processes strong, 
with a downward direction; antorbital foramen circular, with a well- 
developed tubercle on outer lower border. 
KEY £O THE SUBGENERA. 
A. Coronoid process of mandible broad and heavy. 
a. Nasals equal in length to the premaxille 
ee ee Te eee ae POR 7 ee Ce Ammos permo philus 
b. Nasals not so long as the premaxille...Xerospermophilus 
B. Coronoid process of mandible long and slender. 
a. Nasals longer than the premaxille. 
a.’ <sadl Shor, dace aes sete eee ae Callospermo philus 
ib. abaillongy and bushiy ss em eee eee Otospermophilus 
KEY TO THE SPECIES AND SUBSER CESS. 
A. Size small; tail short, narrow. 
a. Upper parts not spotted. 
a.’ Tail beneath white on central portion. 
a.’’ Above grizzled grayish brown and vina- 
CEOUS gatas hee eo ee eee 1. . CO hems 
b.’”” Above pale yellowish brown and white. C. h. saxicola 
C. (Abo Viessniazledyonana tree ot ares ...C. leueurus 
di” A: bOvesinOn’ Stayt or aye eee C. Ll. peninsule 
e.’’ Above grizzled gray and vinaceous ....C. imterpres 
b.’ Tail not white beneath. 
a.’ Above grizzled gray and yellowish 
TOWiie Se bas cate ered cnn: Cree C. tereticaudus 
be Aibowe tayyian COlOT =. eset eee C. t. sonortensts 
c.”’ Above grizzled yellowish brown and 
black |i ca Wlos bs. ee eee C. perotensis 
b. Upper parts spotted. 
a. Above reddish brown 7i2h4 45. eee C. sptlosoma 
b.’ Above russet brown, white spots bordered 
with dtskyox 260) 2.5: Sate ene C. s. micros pilotus 
ce.’ Above dark reddish or yellowish brown. ...C. mexicanus 
di’ “Above pale reddish brown 2s)... se. eee C.m. parvidens 
B. Size large, tail long, bushy. 
a. Tail not over one-fourth total length....... C. madrensts 
b. Tail less than half total length. 
a.’ Tail not annulated. 
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