342 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
on the upper parts and sides of a pale yellowish hoary, instead of being black. The top of the 
head is dark brown, except on the muzzle, which is black;, there is, however, a subterminal 
hand of grayish white, as described. The feet and tail are entirely black. The bases of all the 
hairs in this specimen are almost black. In this, though a male, the teats are distinctly dis¬ 
cernible to the number of four on each side—two on the groin, one inside of the shoulder, and one 
behind the axilla. There are none visible on the belly. 
We thus see that this species varies very considerably in the color of the lower parts, and to 
a less extent in the upper ; nor is the color a question of age, as very large specimens are as 
different as half grown and young ones. The principal variations before me are as follows : 
1. Almost entirely glossy jet black all over. On the back, however, the long hairs have dull 
yellowish rusty tips. The under fur on the back sooty brown at the base, becoming faintly 
yellowish brown towards the end. Hose and chin whitish. (No. 1572.) 
2. General color dusky. The grizzling of the dorsal surface confined mainly to the sides of 
the shoulders. Under fur with light brownish yellow tips. A dark rusty or chestnut suffusion 
round the fore legs. Nose and chin whitish. (No. 847.) 
3. Similar to the last in all respects, but with the black hairs of the belly tipped mostly with 
dark chestnut.. (No. 1571.) 
4. Under parts still more chestnut, though also showing much black ; above, more generally 
yellowish hoary. A still deeper chestnut tinge round the fore legs. (Nos. 854, 1575, 1574.) 
5. Under parts pretty uniform chestnut, the bases of the hairs still dusky. The hairs around 
and between the bases of the fore legs brighter and deeper chestnut. (Nos. 1631, 1573.) 
6. Similar to preceding, but the tail is grizzled like the back, the hairs above and below being 
all finely annulated with brownish yellow, white and dark brown. (Nos. 1392, 1150.) 
As a generalization from these variations, it may be stated that the legs and tail are almost 
always black, (in 1392 the tail is grizzled like the back.) Where the belly is rusty, the region 
round the base of the fore legs is of a deeper chestnut. The upper parts are not pure black in 
any of the specimens before me; where the dorsal surface is hoary, this is most distinct, and 
lightest on the sides of the shoulders, as in Spermophilus douglassii and beecheyi. In all the 
specimens the soles are naked. 
It is worthy of remark that the only specimens enumerated in which the tail is grizzled like 
the back, with the hairs annulated, are those from Wisconsin and Missouri. 
This species, so familiarly known throughout the United States as the woodchuck, or ground 
hog, has been described under several names. There is now no reasonable doubt that the 
Arctomys empetra , so long kept 'separate from the A. monax , is really identical with it, as 
insisted on by Audubon and Bachman. According to these authors, the species ranges from 
Hudson’s Bay to South Carolina, and westward to the Bocky Mountains. It is probable, how¬ 
ever, that at some distance west of the Upper Missouri it is replaced by the species I have 
called A. jlaviventris. 
