Feb., 1912. Mammals of Illinois and Wisconsin — Cory. 175 



Tail more than 2.75 in. (70 mm.) long; total length from 6.87 to 7.50 in. 

 (175 to 190 mm.); tail usually 3.25 to 4 in. (80 to lOO mm.); some 

 specimens show whitish hairs at the anterior base of the ears. Usually 

 distinguished by size and length of tail from P. noveboracensis. 



Canadian White-footed Mouse. 

 Peromysctis manictilatiis gracilis, p. 193. 



Part 2. Under parts mouse brown; upper parts darker brown. 



House Mouse. 

 Mus musculus, p. 176. 



SECTION 2. Tail more than 4 inches long. 



Tawny brown on sides of body; back darker brown; sides of belly tinged 

 with pale brownish yellow; front of upper incisors with distinct lon- 

 gitudinal groove. This species belongs to family Zapodidce and does 

 not properly belong here, but might be looked for in this family by those 

 not familiar with mammals. Jumping Mouse. 



Zaptis hudsonius, p. 247. 



GROUP 3. Total length less than 10 inches; tail less than 2 inches long. 



SECTION 1. Total length more than 5.50 inches; tail more than 1.25 inches 

 long. 

 Tail usually less than 1.60 inches long; dark brown hairs of upper parts 

 tipped with light grayish brown, giving a grizzly effect of mixed light 

 and dark brown hairs; under parts grayish brown; plantar tubercles 

 5; mammae 6. Prairie Meadow Mouse. 



Microtus ochrogaster, p. 218. 



Tail usually more than 1.60 inches long; fur on upper parts softer and darker 

 brown and lacking the grizzly effect of M. ochrogaster; under parts 

 distinctly grayish or plumbeous gray, not brownish gray or gray brown, 

 as in ochrogaster; plantar tubercles 6; mammae 8. Meadow Mouse. 



Microtus pennsylvanicus, p. 2 14. 



SECTION 2. Total length less than 5.50 inches. 



P.\RT 1. Front of upper incisors (front teeth) with distinct groove near 



outer edge. 



•\ l/y Total length usually more than 4.75 inches; tail less than i inch long. 



■-jLJ] Occurs in Illinois and perhaps southern Wisconsin. 



Front view of Cooper's LemmING MouSE.* 



Upper Incisors. _ 



(Enlarged.) bynaptomys coopen, 



and Goss's Lemming Mouse. 



Synaptomys cooperi gossi, p. 233. 



Total length less than 4.75 inches; tail less than i inch long; skull smaller 

 and incisors narrower and smaller than 5. cooperi. Occurs so far as 

 known within our limits only in northern Wisconsin. 



Bangs's Lemming Mouse. 

 Synaptomys cooperi fatuus, p. 237. 



* I have seen no specimens of typical cooperi from Illinois, but intermediates 

 between cooperi and gossi occur in the northeastern part of the state. S. c. gossi 

 occurs in southern Illinois. 



