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 flat, as in Murince, but variously complicated. The zygoma 

 is not deflected as far downward as in Murince, 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 Murince. 



GENUS HYPUD^US ILLIGER.* 



This small genus fittingly introduces the arvicoline group of 

 rodents forming a transition as it does between the Murince or 

 common mouse subfamily and the field mice or Arvicolince. 



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 Murince. 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 Murince). The teeth are 

 otherwise as in the field mice bub less completely broken up 



*ln using this name for the genus lately renamed Evotomys by Coues, we follow 

 Keyserling and Blasius, Prof. Baird and European authors generally. It seems a 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 well ignored in this ease and the above 

 name, which has been more or less fully instated in theIlterAtufinf both continents' 

 retained for this group. 



UHIVBRSITY 



