SQUIRRELS OF MEXICO AND CENTRAL AMERICA 95 



strongly shaded with yellow. Crown and back darker, often becoming 

 blackish along middle of rump and on base of tail ; top of back some- 

 times, and flanks commonly, washed with pale yellowish ; sides of head 

 grizzled gray and dark fulvous, the gray sometimes predominating; 

 ring around eye well marked and varying from buffy white to rich 

 fulvous buffy ; ears dingy gray sometimes suffused with pale buffy ; 

 a scanty basal patch of dull buffy or orange buff sometimes present ; 

 feet and often most of fore legs and entire underparts varying from 

 dark dull buffy yellow to rich orange yellow, sometimes suffused with 

 rusty; hind feet usually a little darker than fore feet; outside of hind 

 legs varying from gray suffused with dull rusty to uniform rusty some- 

 times with a strong tawny rufous shade that extends over inside of 

 thighs ; tail above black, with a wash varying from pale yellowish white 

 to rusty yellow; below with broad median area varying from yel- 

 lowish rusty to dull rusty rufous with a broad indistinct black border 

 and broad edge of pale yellowish, or rusty buffy, the latter colors often 

 forming a wash over entire lower surface. Hairs of back black, with 

 small white or pale yellowish tips and broad buffy or yellowish basal 

 or sub-basal rings. 



Variation. — The amount of individual variation is comparatively 

 small ; the back becomes a little paler or darker, the color on outside 

 of thighs more or less intense, and color of lower parts varies in in- 

 tensity as already described. 



Measurements. — Average of five adults from northern Chihuahua : 

 total length 565.8; tail vertebras 279; hind foot 79.2. 



Cranial characters. — Premolars \. Skull much larger than that of 

 S. oculatus., with audital bullae proportionately smaller. Five adult 

 skulls from western Durango average as follows : basilar length 56.4 ; 

 palatal length 28. 7; interorbital breadth 21.5; zygomatic breadth 

 37.5; length of upper molar series 11.9. 



General notes. — Although the color of Sciurus apache is very 

 much like that of S. ludovicianus, the form of the skull shows that it 

 belongs to the subgenus Ara:osciiir7is, of which S. octilatus is the 

 type. 



During the summer of 1898 we found S. apache common m the 

 mixed forest of pines and oaks on the mountains of western Durango. 

 They live in hollow oaks, entering by a knot hole or broken branch 

 and were rarely seen on the pines. The upper limit of their range 

 overlaps the lower limit of S. diirangi but neither occupies much 

 territory of the other. The type of this fine squirrel came from the 

 region once occupied by the Apache Indians for whom it was named. 



Proc. Wash. Acad. Sci., May, 1899. 



