FAMILY MURID^. 83 



Total length, , ft-"0. Length of hind feet, 1 • 5. 



Length of head, I'O. Ditto of whiskers, 1'5. 



Ditto of body, 2-5. Ditto of tail, 2-5. 



Ditto of fore feet, • 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, givipg it the name of emmonsi, 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. Lacefede. 



Grinders flat on their crowns, the enamel forming angular ridges on the surface. Ears 

 furry. Tail round and hairy, shorter than the body. 



Obs. This genus, which was first separated from Mus by Lacepede, comprises many 

 species knowrn 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 agTurius has small ears, a constant black line on the back, the thumb with a nail, tail half 

 the length of the body, etc. 



