SQUIRRELS OF MEXICO AND CENTRAL AMERICA 45 



Distributio7i. — Mixed pine and oak forests of Upper Austral zone 

 on east and north base of the Cofre de Perote and adjacent eastern 

 slope of the Cordillera near Las Vigas, Vera Cruz (alt. 6000-Sooo ft. ) . 



Characters. — Differs strikingly from typical aureogaster in having 

 well marked nuchal and rump patches of yellowish brown or rufous 

 brown; the underparts gray or gray washed with rufous; tail heavier 

 and more bushy; pelage softer. Teats : p. i a. |- i. \. 



Color. — Nuchal and rump patches strongly marked, varying from 

 dark yellowish brown to dark rusty red, washed with black, extending 

 forward as a paler area along sides of head to enclose ears and eyes ; 

 rest of upperparts including nose and fore crown, fore feet, outside 

 of legs and sides of body, dark grizzled iron gray, usually with rusty 

 or pale rufous subterminal rings on hairs of back and sides ; hind feet 

 varying from black, slightly grizzled with gray, to dark iron gray ; 

 chin, throat and cheeks dingy gray ; rest of underparts varying from 

 pale gray to gray washed with rusty red ; tail at base like back, rest of 

 tail above black thinly washed with white ; below, with a median band 

 varying from pale rusty yellowish to dark ferruginous, bordered with 

 a black band and edged with white ; ears usually like nuchal patch but 

 sometimes grayish and sometimes with a black border ; basal patch 

 dingy white, present in winter, usually absent in summer. Hairs on 

 back black, with conspicuous white tips often mixed with others hav- 

 ing pale rufous subterminal rings. 



Variation. — The series of this form and of aureogaster show per- 

 fect intergradation although the two extremes are strikingly different. 

 Some specimens taken below Las Vigas have the ferruginous of the 

 underparts somewhat grizzled with gray and more dingy than in 

 aureogaster. The black on the lower surface of the tail varies from 

 a narrow border to a broad band which reduces the median area to a 

 narrow line. Some specimens show 3 or 4 distinct black and rusty, 

 or reddish, annulations on lower surface of tail, giving a grizzled ap- 

 pearance which does not occur in either aureogaster proper or hypo- 

 ■pyrrhus. No melanistic specimens seen. 



Measure?7ie?tts. — Average of 5 adults from type locality: total 

 length 504.6; tail vertebrae 249.2; hind foot 68.8. 



Cranial characters. — Premolars \. Skull indistinguishable from 

 that of typical aureogaster. Four adult skulls from the type locality 

 average: basal length 52.5 ; palatal length 26.1 ; interorbital breadth 

 19.7; zygomatic breadth 34.4; length of upper molar series 11.2. 



General jzotes. — In several characters this subspecies agrees with 

 the description of S. nigrescens Bennett, but after comparing a speci- 



