MAMMALS OF MINNESOTA. 179 



Hesperomys austcrus BAIRD, Proc. Acad. Nat. Sci. Phila., 1855; Mam. N. 

 Amer., 1857. 



COOPER & SUCKLEY, Nat. Hist. Wash. Ter., 1860. 



Hesperomys boylii BAIRD, Proc. Acad. Nat.Sci. Phila., 1855. Mam. N.A., 1857. 

 Hesperomys gambeli BAIRD, Mam. N. A., 1857: Pac. R. R. Rep., 1859. 



NEWBERRY, P. R. R. Rep., 1857. 



COOPER & SUCKLEY, Nat. Hist. Wash. Ter., 1860. 



The white-footed or deer mouse is familiar to every farmer's 

 boy, and claims admiration, not only on account of its graceful 

 form and spirited appearance, but by its pretty though subdued 

 coloration and sprightly movements. The soft brown pelage 

 of the upper parts contrasts nicely with the pure white of the 

 feet and under parts. The origin of the name deer mouse is 

 found partly in the fawn color which is the normal color of the 

 back and partly also in the long leaps by which the mouse es- 

 capes its pursuers. In the young the shade is less bright and 

 is more like that of the house mouse, while the dorsal colora 

 tion extends downward on the outside of the legs. That the 

 animal is subject to interminable variations in color is seen from 

 the long list of synonyms given. A full discussion of the value 

 of specific characters based on such varieties of coloration may 

 be found in Coues' article on this species in the monographs of 

 N. A. Rodentia, already frequently referred to. It may be ad- 

 mitted without discussion that the specific identity of the names 

 united above is settled once for all by that author's careful 

 revision. Our Minnesota specimens, when adult, are remarka- 

 bly uniform, and present no noteworthy variations. The upper 

 parts are a warm brown as far as well down upon the shoulder 

 and hips. The back is considerably darkened by numerous 

 nearly black hairs while the tail is dark brown above and pure 

 white below. The thighs are gray. The ears are dark with a 

 white margin. There is a dark spot at the base of the whisk- 

 ers which are themselves black. The size of this species varies 

 somewhat, but the chief differences are in the proportional 

 length of tail and body. 



For Minnesota the following measurements are typical for 

 the female: 



Total length 7.0; tail 3.4; body 3.6; hind foot 0.9; fore-fuot 

 0.4; span of hind legs 4.4; of fore legs 3.4; nose to eye 0.55; 

 nose to ear 1.0; hight of ear 0.7. 



The length of the male is less by half an inch than in the 

 female, the proportions remaining about the same. 



According to Coues the averages of eighty specimens from 

 Massachusetts are as follows: 



