FAMILY MURID. 83 
Motallengthy, 22> essoce as 6:0. Length of hind feet, ..... LOGY. 
Length of head,......--- 10; Ditto of whiskers, ....... es: 
Dittoror body, 222 5=-)s-—< 225. Dittonor tatlsae see = acces Die 
Ditto of fore feet, .....-. 0'8. 
This little mouse, from the distribution of its colors, and its slender proportions, has a deli- 
cate and beautiful appearance. It is very agile, jumping in the manner of the deer-mouse ; 
and is called, in common with that animal, the jumping mouse. It seems to prefer forests 
and wooded places, but is often found in meadows or cultivated grounds, where grain and 
seeds of grasses abound. When this mouse was first submitted to me, I referred it to the M. 
agrarius of Godman ; but upon consulting the original description, it was plainly evident that 
it could not be referred to that species, although Godman evidently had the jumping mouse in 
view when he drew up his description.* I had not at that time the work of Richardson to 
refer to, and hastily pronouced it to be new, giving it the name of emmonst, after the eminent 
naturalist who had first brought it to my notice. 
The Jumping Mouse is found in every part of the State, and is said to build its nest in trees. 
In the northern regions, according to Richardson, it becomes an inmate of the dwellings at 
the fur establishments, and makes hoards of grain in various places, such as the pocket of a 
coat, a shoe, etc. We have never heard of its entering dwellings in the cultivated portions of 
our State, but this is probably owing to the presence of the cat, or of rats. It is found from 
Hudson’s Bay to Pennsylvania, and through the Western States to the mouth of Columbia 
river. 
GENUS ARVICOLA. Lacépéde. 
Grinders flat on their crowns, the enamel forming angular ridges on the surface. Ears 
furry. Tail round and hairy, shorter than the body. 
Oss. This genus, which was first separated from Mus by Lacépéde, comprises many 
species known under the vague names of Field Mice and Field Rats; all, however, differ- 
ing from the Mice proper, by the structure of their teeth, and. the length and hairy covering 
of the tail. The species are numerous in the United States, but have not yet been sufficiently 
observed and discriminated. 
* According to Erxleben, p. 398, the agrarius has small ears, a constant’black line on the back, the thumb with a nail, tail half 
the length of the body, etc. . 
