238 Field Museum of Natural History — Zoology, Vol. XI. 



Specimens examined from Wisconsin and adjoining states: 

 Wisconsin — Solon Springs, Douglas Co., i; Sayner, Vilas Co., i; 



Lac Vieux Desert, Vilas Co., i; Conover, Vilas Co., 3 = 6. 

 Minnesota — (N. M.) Elk River, i ; not typical but approaching fatuus. 

 Michigan — (B. S.) Ann Arbor, 2; intermediate between fatuus and 



cooperi. 



^ ^ 



Synaptomys cooperi 



Area of Intergradation 



(^Specimens e^tamlned 

 S. C X''"^' O Records, 



Map illustrating the supposed distribution of Lemming Mice belonging to the subgenus Synap- 

 tomys, which occur in eastern United States. The map is provisional, as the ranges of the various 

 forms have not been determined. No attempt has been made to include all records east of Indiana 

 and Michigan. 



Synaptomys cooperi Baird. (Mammals N. Amer., 1857, p. 558.) Type locality — 



Unknown; supposed to be New Jersey. Color, sepia to tawny brown (more or 



. less variable) mixed with scattered black hairs on back; hairs on under parts 



plumbeous, with whitish tips; mammae 6. Total length, about 4.75 in. 



(120 mm.); tail vertebrae, .70 in. (17.5 mm.); hind foot, .72 in. (18 mm.). 



Synaptomys c. fatuus Bangs. Type locality — Lake Edward, Quebec, Canada. 

 Similar to cooperi, but averaging smaller and somewhat darker than cooperi; 

 skull smaller and upper incisors shorter and narrower. Occurs in northern 

 Wisconsin and northward. 



Synaptomys c. gossii (Merriam). Type locality — Neosho Falls, Woodson Co., 

 Kansas. Size averaging larger than cooperi and color more reddish brown; 

 skull larger and rostrum narrower; smaller audital bullae. The brain case 

 in adult specimens is both actually and relatively longer than cooperi, 



Synaptomys c. helaletes (Merriam). (Proc. Biol. Soc. Wash., X, 1896, p. 59.) 

 Type locality — Dismal Swamp, Norfolk Co., Virginia. Similar to cooperi, 

 but skull somewhat longer and heavier; tail shorter and feet larger. "Similar 

 to 5. cooperi, but with larger head and feet, longer tail, much broader rostrum 

 and mandible, and larger and more massive skull and teeth" (Merriam). 



