134 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
The tail is rather short in its proportions, scarely more than half as long as the head and 
body. It is, however, remarkably dense and bushy, being made up principally of under fur, 
instead of having its contour determined by the long hairs. It is nearly cylindrical, or slightly 
depressed, with a truncate and rounded tip, and is slightly contracted at the base. 
There are no strongly marked contrasts of color in this diminutive fox. The entire upper 
parts and sides extending low down on the thighs and shoulders, are conspicuously grizzled 
with pale grayish white and brownish yellow, mixed with a little dark brown or black. The 
under fur in these regions is light plumbeous at base, and light brownish chocolate yellow at 
tip ; these tints becoming paler towards the sides. The long stiffer hairs are dark brown, 
(more reddish at the extreme tip,) and broadly annulated near the tip with yellowish grey 
white ; there is, however, an occasional hair that is entirely black. The under fur on the top 
of the head has more reddish on the terminal portion. The under parts, generally, for their 
entire width, as well as the inside of the limbs, are yellowish white. On the sides of the neck 
and body, extending some distance up behind the shoulders, the hairs are of a pale reddish 
yellow, without annulation, this color also tinging strongly the fore arm and posterior face of 
the hind leg ; the rest of the legs, except as described, is of a pale brownish white. There is 
a dusky tinge around the lips, and a patch of the same between the eye and the nose, above 
the insertion of the whiskers, which are themselves black. The ears are uniform brownish 
yellow on their convexity; anteriorly yellowish white. 
The tail, in general tint, resembles the back, except that there is no distinct annulation, the 
prevailing hue being a yellowish gray. There is a considerable amount of black on the tips of 
the hairs, but this is much less conspicuous than in the red and gray foxes. There is most 
black at the truncate tip. There is nothing corresponding to the white tuft of the red fox. 
The under surface of the tail is tinged with yellowish red. 
The specimen described above is in very full fur, having probably been taken in the depths 
of a Fort Union winter. The colors differ slightly from those given by some other authors, 
owing possibly to season ; and the animal itself appears to have been of unusually large size, 
and very old, judging by a comparison of its skull with a considerable number of separate 
skulls sent by Dr. Hammond from Fort Kearny. Its distinctive features are so striking as to 
render it quite unnecessary to compare it with other American foxes ; according to Richardson, 
its nearest relative is the Canis corsac of Siberia. It comes nearer in appearance to the gray 
fox than the red ; it lacks, however, the bright chestnut of the ears and sides of the neck, the 
black muzzle, the predominant badger gray and black of the back, the well defined black dorsal 
stripes and tip to the tail, which, in the swift fox, besides, is very much denser, fuller, more 
truncate, and without the concealed mane of stiff hairs in the upper surface of the tail. The 
skulls of the two animals are widely different. 
Measurements of No. 59. 
Inches. 
Length, from nose to tail___ 
24 
Tail to end of vertebrae____ 
9 
Tail to end of hairs______ 
10* 
Width of tail flattened horizontally___ 
i 6 
Height of ear above notch_ 
If 
