502 



REPORT OF STATE GEOLOGIST. 



seldom live in the clean, smooth pastures or meadows and never 

 live in the cultivated fields unless they can find harboring places 

 of some sort where they can make their homes. They are easily 

 captured in ordinary mouse traps baited with cheese or dry oat- 

 meal and set hear the holes leading to their nests. 



PEROMYSCUS MANICT'LATT'S BAIKDI (Hoy and Keiinicott). 

 PRAIRIE WHITE-FOOTED MOUSE. 



Mvs hairdi Hoy and Kennieott in Kennicott, IT. S. Patent Office 



Report for 1856, pp. 92-95, PL XI, 1857. 

 Hesperomys michiganeiisis Baird, Mam. N. Amer., p. 476, 1857. 

 Calomys michiganeiisis Everniann and Butler, Proc. Ind. Acad. 



Sci. for 1893, p. 139. 

 Peromyscus michiganensis Allen, Bull. Am. Mus. Nat. Hist., 



Vol. VIII, p. 238, 1896. 

 Peromyscus maniculatus hairdi Osgood, N. Am. Fauna No. 28, 



p. 79, 1909. 



Diagnostic characters. — Smaller and bluer (less brownish) than 

 P. leucopus and with smaller ears and feet. 



Description. — The color differences between michiganensis and 

 leucopus are not easily described, but they are none the less evi- 

 dent. The duller color seems to be due, in part, to the greater 

 number of plumbeous tipped hairs, in part to the fact that the other 

 color is fawn rather than russet. The dark stripe along the mid- 

 dle of the ])ack is also more plumbeous and this color is continued 

 along the dorsal side of the tail. The tail is more thickly haired 

 than in the common deer mouse and the dark color of the dorsal 

 third is very sharply marked off from the white ventral two- 

 thirds. The hind foot is shorter and more slender, an important 

 character in distinguishing michiganensis from young leucopus, 

 as the foot of a young mouse is proportionally larger than that of 

 an adult, and the foot attains the maximum size before the animal 

 is fully adult. 



Measurements. — An adult female from Newton County meas- 

 ured 135 mm. (5 6/16 in.) in total length; tail, 60 mm. (2 6/16 in.) ; 

 hind foot. 15 mm. (10/16 in.). The corresponding measurements 

 of an Ohio (Jounty specimen were 137 mm. (5 7/16 in.) ; 57 mm 

 (2 4/16 in.) ; 17 mm. (11/16 in.). 



Hk}dl and teeth. — The skull is both shorter and more slender 

 ill I(i(<'()j)iis, the incisive r(»i';niiiiia arc n^latively wider, 



