MAMMALS OF MINNESOTA. 193 
.are worn off the pattern does not vary greatly with use. In 
almost all the species the molars are rootless. The palate is 
not fiat, as in Murine, but variously complicated. The zygoma 
is not deflected as far downward as in Murine, and it is not 
emarginate at its anterior origin. The nasals are broad and 
short. The angle of the mandible is arched. The scapula is 
narrow, with long, slender acromium. The proportions of the 
limb bones are different from those common in Murine. 
GENUS HYPUDASUS ILLIGER.* 
This small genus fittingly introduces the arvicoline group of 
rodents forming a transition as it does between the Murine or 
common mouse subfamily and the field mice or Arvicoline. 
The separation of the genus from other field mice is a matter 
of convenience as well as morphologically demanded. The 
very few species are all inhabitants of the northern hemisphere 
and are so closely related that they might without serious im- 
propriety be reduced to varieties of a single circumpolar 
species, Mus rutilus Pallas. 
The external form is sufficiently like that of our common 
field mouse, Arvicola riparius, but the color is bright, all these 
mice deserving the adjective ‘‘red-backed”. The red-backed 
mice are inhabitants of the woods as distinguished from the 
prairie mice and those so disposed may see in the color illus- 
trations of protective coloration. The wood mice frequent 
decaying trees, the pulverent wood surrounding which com- 
monly has a color very like that of the mice. The prairie mice 
are exposed to greater danger and have a color not unlike that 
of the sear grasses or the earth. 
The genus is so essentially arvicoline that the diagnostic 
features may take the form of points varying from that type 
in the direction of the Murine. In form arvicoline, but rather 
less slender and with longer ears. Colors bright or, at least, 
strongly red. Molars each with two roots (instead of rootless 
as in Arvicola or fully rooted as in Murine). The teeth are 
otherwise as in the field mice but less completely broken up 
*In using this name for the genus lately renamed Evotomys by Coues, we follow 
Keyserling and Blasius, Prof. Baird and European authors generally. Itseemsa mis- 
fortune that in nomenclature as well as in more vital matters there should be no 
articulation between the scientific labors of the two continents. Dr. Coues has in the 
case of this genus (as well as frequently elsewhere) shown the intimate relations 
between the mammals of Europe and North America. It is therefore a positive misfor- 
tune if the same group bears different names on the different sides of the Atlantic. It 
seems that the technicality involved might be wellignored in this case and the above 
name, which has been more or less fully instated in the literature of both continents: 
retained for this group. 
