SCIURUS. 95 



B. Size large, total length over 450 mm. 



a. Premolars ^. 



I 1 



a.' Belly buffy or yellowish. 



a." Back gray. PAGE 



a.'" Median area on back black; belly 



usually deep buff 5. oculatus 107 



b.'" Median area on back washed with 



blackish; belly buffy whitish 5. toluca 107 



b." Back yellowish gray. 



a.'" Belly rusty yellow; total length over 



500 mm 5. apache 1 10 



b.'" Belly more dingy yellow; total 



length under 500 mm 5. r. texensis 1 10 



b/ Belly white. 



a." Back golden buffy or yellowish , overlaid 



with grizzling of black and white 5. nayaritensis 108 



b." Back gray. 



a/" Back uniform gray or grayish brown ; 



ears gray; total length under 500 mm S. alleni 108 



b/" .Back gray washed with yellowish on 

 nape and back of shoulders; ears 

 rusty. 



a. 4 Total length under 500 mm S. arizonensis 109 



b. 4 Total length over 500 mm S. a. huachuca 109 



b. Premolars ^. 



a.' Nape patch strongly marked, rump patch 



present or absent, 

 a." Belly gray, rump patch well marked; 



back dark gray 5. a. frumentor 117 



b." Belly white or buffy. 



a.'" Rump patch poorly defined or absent. 



a. 4 Back dull whitish ; belly white or buffy . 5. socialis 1 23 



b. 4 Back pale gray; belly white or buffy 



5. p. hernandezi 1 1 8 



b.'" Rump patch well defined. 



a. 4 Middle of back gray; feet gray or 



blackish; belly white S. p. colimensis 119 



b. 4 Middle of back whitish ; feet whitish ; 



belly white or buffy 5. s. cocos 124 



c." Belly rufous. 



a/" Feet gray or blackish. 



a. 4 Ribs, and sometimes shoulders, rufous. 

 a. 5 Back pale gray; top of head iron 



gray 5. aureigaster 115 



