RODENTIA—SCIURINAE—SCIURUS FOSSOR. 265 
of the circumference, theentire under parts being pure white. There is not the slighest trace of any 
darker line of separation on the flanks. The upper surface of the feet and exterior of the limbs 
are like the back; the paws perhaps lighter, but still grizzled. The inner edge of the hind foot, 
also, is nearly uniform dull whitish. The lower parts of the cheeks and side of the muzzle are 
greyish white, less pure than on the belly. The woolly tuft at the base of the ear, and usually 
the convexity or back of the ear itself, are light chestnut, forming a very conspicuous feature. 
The tail is a mixed gray, black and white. Beneath, it is grizzled; above, black predomi- 
nates, with some white on the outside; on the side the white is very conspicuous, furming a 
distinct white border. The inferior hairs are grayish white, with four or five annulations of 
black, about the width of their interspaces. The same condition prevails pretty much on the 
rest of the tail, with the exception that the subterminal annulation is much broader and 
entirely black, and on the sides the terminal white is also very long. 
There is no appreciable difference in a number of specimens of this squirrel before me from 
different localities; much less than usual in squirrels. One from Fort Tejon has a smaller body 
in proportion to its tail than the rest; but the skin has probably shrunk considerably in alco- 
hol, and the animal itself was quite young, as shown by the skull. This is the only one in 
which there is no chestnut on or behind the ear, the woolly tuft there being dirty whitish. One 
specimen (609) shows a slight wash of rusty on the back, and the hind feet are sooty black, 
slightly grizzled. This is the most decided variation I have noticed. Winter specimens have 
the soles hairy, except on the tubercles, while summer ones have them naked. 
Skull.—The skull of this species appears rather more slender and elongated than that of the 
S. carolinensis or the fox squirrel of the Mississippi; its closest relationships, as to shape, are 
with the S. vulpinus, which it nearly equals in size. It has, however, a longer muzzle and the 
zygomatic arch set further back. ‘An old skull has four distinct upper molars and the stumps 
of the anterior fifth one, broken down to the level of the socket. In several younger ones this 
small molar is well developed and considerably larger than in S. carolinensis, the crown having 
a compressed central tubercle and a distinct valley on either side. 
This species is mentioned by Lewis & Clark, under the name of “‘the large gray squirrel,’’ as 
occurring near the Dalles of the Columbia, and they fully appreciated its difference from the 
squirrels of the eastern States. It is a little singular that an animal described with such detail 
by these authors should not have been named by the earlier writers, like Ord, Rafinesque, 
Harlan, and others, when all the other species mentioned in the narrative of the expedition 
were so promptly introduced into the systems. 
I am not without a strong suspicion that the Sciwrus leporinus of Audubon and Bachman 
may prove to be the same with the S. fossor, in which case it will, of course, take precedence. 
_ The only point in the description which cannot be readily referred to S. fossor of Peale isin the 
color of the back, which is said to closely resemble that of the English hare (probably Lepus 
timidus) in its brown tints. But for this I would be inclined to consider it as a young specimen 
of S. fossor, as in the most immature one I have seen (480) the downy space on the back and 
base of the ear was whitish instead of chestnut. Indeed, this same specimen I had unhesi- 
tatingly labelled S. leporinus before the opportunity was afforded of examining adult animals. 
This squirrel inhabits abundantly the whole mountain region of California, from San Diego 
as far north as the Columbia River at the Dalles; it does not appear to cross this river. The 
extreme limit of its distribution south and east is not yet ascertained. As far as I can learn, 
however, it is the only large species found within the region inhabited by it; and I have na 
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