68 RECONNAISSANCE FROM CARROLL, MONTANA, 
the steamer, or feeding on the tender shoots of the cottonwood and willow. They were by no 
means shy, and would sometimes permit the vessel to pass within a few yards of them without 
taking to the water. 
The streams in the mountains through which we passed were sometimes dammed by the 
Beavers for miles, and the backwater spreading out over the level valleys makes wide ponds. 
These in the course of time are partially filled up with the mud carried down by the stream, and 
when this takes place are deserted by the Beavers, which move away and build another dam some- 
where else. As the pond fills, a rank growth of rushes and underbrush springs up, and before long, 
what was a pretty little lake has become an impassable morass. 
The value of the fur of the Missouri River Beaver is diminished by the same causes spoken of 
in reference to that of the Otter. 
SACCOMYID. 
24, THOMOMYS TALPOIDES, (Rich.) Baird. 
GOPHER. 
An individual of this species was taken among the high mountains near the head of Gardiner’s 
River. It was running over the snow-drifts when captured. 
MURIDZ. 
25. ZAPUS HUDSONIUS, Coues. 
JUMPING MOUSE. 
This species was observed several times in the Bridger Mountains, and again on Cascade 
Creek near the Yellowstone River. 
26. MUS DECUMANUS, Pallas. 
Brown Rat. 
The common Wharf-rat is sufficiently abundant in all the settlements on the Missouri River to 
be a great nuisance and to do considerable damage. In the trader’s store at Fort Peck, they were 
very numerous, so much so that the trader told me that he had recently poisoned one hundred and 
fifty in one week. 
27. MUS MUSCULUS, Linn. 
House MOovss. 
Abundant in towns and large settlements, but in isolated ranches replaced by the following 
species. 
28. HESPEROMYS LEUCOPUS SONORIENSIS, LeConte. 
WESTERN WHITE-FOOTED MOUSE. 
This species was very abundant along the North Fork of the Musselshell River and along the 
‘Yellowstone. In many places, they had deserted the woods and fields and taken to the ranches, 
where they are quite as annoying as the common House Mouse. 
29, ARVICOLA RIPARIA, Ord. 
MEADOW MOoUsE. 
Very common along the Yellowstone River. 
30. FIBER ZIBETHIOUS, (L.) Ouv. 
MUSKRAT. 
Abundant on streams flowing into the Missouri. 
