SQUIRRELS OF MEXICO AND CENTRAL AMERICA 33 



fined this group its members were confused with the species of the 

 subgenus Guerlinguetus Gray {Macroxtis Cuvier) which are charac- 

 terized by a single upper premolar. 



KEY TO SPECIES AND SUBSPECIES. 



Size large, total length over 450 mm. 

 Premolars -i- 



Belly bu^y or yellowish 

 Back gray 



Median area on back black ; belly usually deep buff 



oculatus p. 88. 

 Median area on back washed with blackish ; belly 



buffy whitish tolucce p. 89. 



Back yellowish gray 



Belly rusty yellow; total length over 500 mm. 



apache p. 94. 

 Belly more dingy yellow; total length under 500 



mm liTnitis p. 97. 



Belly white 



Back golden buffy or yellowish overlaid with grizzling 



of black and white nayaritefisis p. 93. 



Back gray 



Back uniform gray or grayish brown ; ears gray ; 



total length under 500 mm alleni ■^. 91. 



Back gray washed with yellowish on nape and 

 back of shoulders; ears rusty ; total length over 



500 mm huachuca ^. 96. 



Premolars f 



Nape patch strongly marked, rump patch present or absent 



Belly gray ^ luhite, or buffy 



Belly gray, rump patch well marked; back dark 



gray Jrumentor p. 44. 



Belly white or buffy 



Rump patch poorly defined or absent 



Back dull whitish ; belly white or buffy 



social is p. 63. 

 Back pale gray ; belly white or buffy 



hernandezi p. 48. 

 Rump patch well defined 



Middle of back gray ; feet gray or black- 

 ish ; belly white colimefisis p. 52. 



Middle of back whitish ; feet whitish, belly 



white or buffy cocos p. 65. 



Belly rufous 



Feet gray or blackish 



Ribs and sometimes shoulders rufous 



Back pale gray ; top of head iron gray 



aureogaster p. 38. 



