58 Merriam The Lemmings of the Genus Synaptomys. 



Subgenus SYNAPTOMYS Baird. 

 Synaptomys cooperi Baird. 



Synaptomys cooperi Baird, Mammals N. Am., pp. 556-558, 1857. 



Coues, Proc. Acad. Nat. Sci., Phila., p. 194, 1874; Monog. N. Am. 

 Rodentia, pp. 235-236, 1877. 



Quick and Butler, Am. Naturalist, XIX, 113-115, Feb., 1885. 



Merriam, Proc. Biol. Soc. Wash., VII, 175-177, Dec., 1892. 



Bangs, Proc. Biol. Soc. Wash., IX, 99-104, April, 1894. 

 Synaptomys stonei Ehoads, Am. Naturalist, XXVII, pp. 53-54, Jan. 11, 1893. 



Type locality unknown ; probably northern New Jersey or southern New 

 York. 



Geographic distribution. Boreal and parts of Transition zones from Min 

 nesota eastward to eastern Massachusetts and south to Iowa, Indiana, 

 and Maryland, and in the mountains to North Carolina and Tennessee. 

 South of the Boreal zone it appears to be confined to cold sphagnum 

 swamps, which give it a boreal atmosphere. 



General characters. Similar in size and general appearance to Microtus 

 pennsylranicus, but tail very much shorter. Contrasted with Synaptomys 

 helaletes the feet are smaller and the rostrum, mandible, and upper incisors 

 are much narrower and less massive. 



Color. Upper parts grizzled gray and yellowish brown abundantly 

 mixed with black-tipped hairs ; under parts soiled whitish, the plumbeous 

 under fur showing through ; tail bicolor ; brownish above, whitish below. 

 In the adult the color of the back varies from pale yellowish brown to 

 almost rusty, always ' grizzled ' by a bountiful admixture of black-tipped 

 hairs. In the young the color is at first very dark, almost blackish slate ; 

 it then becomes grayish brown and approaches sepia before taking on the 

 yellowish brown of the adult. 



Cranial and dental characters. Contrasted with 

 ^' ne ^ etes ^ rom Dismal Swamp, the skull and 

 teeth of S. cooperi are smaller and weaker, the 

 zygomata more bowed outward, the rostrum and 

 mandible very much narrower, the nasals nar 

 rower posteriorly, and the brain case shorter. 

 FIG. 2. Enamel pattern of Measurements. Average of 4 specimens from 

 upper and lower molars ^nn Arbor, Michigan: total length, 118; tail 



in Synaptomys cooperi. vertebrffi| 17>5 . hind footj 18> Average of 2 



from Roan Mountain, North Carolina: Total length, 121 ; tail vertebrae, 

 20 ; hind foot, 19.5. 



Synaptomys fatuus Bangs. 

 Synaptomys fatuus Bangs, Proc. Biol. Soc. Wash., X, 47-48, March 7, 1896. 



Type locality. Lake Edward, Quebec. 



Geographic distribution. Hudsonian zone from Lake Edward, Quebec 

 (and probably much farther west), to Victoria county, New Brunswick, 

 and Godbout, Quebec. Limits of range unknown. 



General characters. Similar to S. cooperi, but slightly smaller; skull de. 

 cidedly smaller, with much narrower upper incisors. 



