TO YELLOWSTONE NATIONAL PARK. 67 
and luxuriant undergrowth of the mountains. They are very gentle and unsuspicious, and would 
play about in the most unconcerned manner while I was standing within a few feet of them. 
Although by no means tree-climbers, in the strict acceptation of the term, I often saw them, 
while at play or when frightened, ascend the pines to a height of 20 or 30 feet. It would seem 
that they are not exclusively vegetarian in their diet; for I interrupted one of them while making 
a meal of the dried carcass of a Hesperomys. It sat up, holding the food in its fore feet in the 
ordinary manner, and gnawing the meat from the back and shoulders. ‘No doubt, in some localities 
it feeds, partially at least, on grasshoppers, as many of the small rodents of the West are known 
to do. 
19. SPERMOPHILUS TRIDECIM-LINEATUS, Mitchell. 
STRIPED PRAIRIE SQUIRREL. 
This species was common everywhere on the prairies. When anything unusual attracts its 
attention, it raises itself up on its haunckes to examine the object of its curiosity. As this approaches, 
the squirrel gradually lowers itself until at last it is quite flattened out upon the ground. In this posi- 
tion, if the eye is removed from it for a moment, it is very difficult to find it again, as its colors 
harmonize admirably with the yellowish gray of the soil. 
20. SPERMOPHILUS RICHARDSONII, Cuv. 
RICUARDSON’S GROUND SQURREL. 
This species was not seen until after we had passed Camp Lewis in Montana. Along the 
North Fork of the Musselshell River it was abundant in the valley, and it was observed in con- 
siderable numbers about Camp Baker and Fort Ellis. 
Ia their habits, they resemble the Prairie-dog (Cynomys) more nearly than any other species 
with which Iam acquainted. They live in communities, act as do the Prairie-dogs when approached, 
and are equally hard to secure when shot near the entrance of their burrows. A young one, killed 
with a charge of fine shot at short range, moved himself over two feet along the smooth sur- 
face of a flat rock, on which he had been lying when shot, by convulsive pushes of his hind feet. 
After I had taken him in my hand, these kickings continued for half a minute or more, although 
the animal could not have been conscious after the shot struck him. 
I several times saw the young of this species playing with one another very prettily. One 
standing over the other would hold him down and pretend to bite his head and neck, just as we 
often see young puppies play together. 
At Camp Baker, there were many of these animals in and about our camp, and they soon 
became very tame. Often'they would come to the open tent-door, and, sitting on their haunches, 
would watch the occupants with an appearance of the greatest curiosity. We often tried to catch 
them alive, but were never successful. They would always manage to slip into some hole that we 
did not know of, just as our hands were on them. Between Fort Ellis and Bozeman there is quite 
a large settlement of these animals, and they were more tame here than at any other locality where 
we met with them. 
21. CYNOMYS LUDOVICIANUS, Baird. 
PRAIRIE-DOG. 
Quite abundant on the plains near the foot of the mountains. 
22, ARCTOMYS FLAVIVENTER, Bach. 
WESTERN WOOD-CHUCK. 
Common in the mountains, but rather a shy species, more often heard than seen. 
23. CASTOR CANADENSIS, Kuhl. 
BEAVER. 
While ascending the Missouri, we saw the houses and “slides” of the Beaver very frequently, 
and often, just at evening, the animals themselves were observed, sitting on the banks gazing at 
