36 UNITED STATES AND MEXICAN BOUNDARY, 



the tarsus^ (or on the under surface of the metatarsuSj) although the hairs encroach somewhat 



on the outer edge. 



The tail is a little longer than the hody. It is not hushj^ hut rather slender, and the hairs 

 are not full, as in most of the other large species. 



The general tint of the upper parts and sides of the hodj and limhs is a mixed lead color and 

 ash grey, with some scattered hlack hairs. The whole hack from the nape to the hase of the 

 tail is of a deep and well-defined chestnut brown ; this color being not a mere dorsal stripe, but 

 covering a space the width of the tail. The sides of the head and the ears are grizzled ash. 

 The under parts, the eyelids, and the upper surfaces of the feet are of a rather clear white, the 

 latter somewhat grizzled. The colors of the sides and belly are separated by a dusky line, as in 

 the chickarees. There are some scattered chestnut hairs in the sides. The tail is entirely 

 white and black ; the central portion black above, white beneath, with white margin and tip j 

 but all the black hairs are tipped with white. The hairs of the tail beneath are uniform white; 

 on the sides they are mostly white, mixed with a few black ones ; on the upper portion they are 

 black at the base, then white, then black and tipped with white, the black predominating. In 

 one specimen, however, the supra-caudal hairs are glossy black, except at their tips, which is 

 the case in both with the hairs at the end of the tail. 



Two specimens, male and female, of this species were collected by Mr. Clark at the Copper 

 mines of the Gila, in the spring season. They were found among the pines. 



Length to root of tail, 12 ; tail to end of vertebrae, 11 ] tail to end of hairs, 12.75 ; greatest 

 width of tail, hairs extended, 4 50 ; hind feet from heel, 2.60 ; hind feet, naked part of soles, 

 2.08; height of ear above skull, .84; height of ear behind, 1.33; length of skull, 2.40; 

 breadth across zygomata, 1,33. 



This species bears a very close resemblance to ^S'. aberii^ and may prove to be the same, 

 although there are apparent differences. The most striking characteristic is the absence of the 

 beautiful ear tufts of S. aherti. Some of our squirrels which have smooth ears in summer are 

 tufted in winter, but as the Copper mine specimens were caught in spring, it is not likely that 

 they are ever tufted. The tufts, too, of ^. aherii are long hairs growing from the very margins 

 of the ears and project an inch beyond. The interior surface of the ear and a wooly space at 

 their posterior bases are greyish white in S. casianonotiis. Great differences again are visible 

 in the tail, which in the latter is nearly pure black and white ; the inferior hairs pure white, 

 those on the upper surface and upper part of the sides are black, with white tips, greyish at the 

 base. In S. aherti all the hairs above are annulated several times with dark brown and greyish 

 white, presenting no decided impression of either color, except towards the end of the tail. The 

 tail here is likewise much more bushy. 



S.fossor is without the dorsal stripe and the dark lateral line. The tail is much fuller and 

 more bushy ; the hairs beneath the tail are finely annulated ash grey and black, without any 



em 



The feet also are dark colored. 



The skull of this species is of very nearly the same size with that of S. caroUnensis, from 



Carlisle. Like this 



molar, making five, but this is 



considerably larger in the New Mexican animal, and has a central tubercle on the crown, 

 with a lateral valley on either side, as in the spermophile. There are no 



other 



importance. 



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•J 



