Tlw Lemminf/s of the Genus SyjiaptoiDi/s. 57 



tomys innuitus.^'' The characters that separate it troni Si/naploviys 

 pro})er seem of subi>;eneric rather than generic weight, and in tlie 

 present paper Mictomy^i is treated as a subgenus of Syunptotiuj^. 



In 1S74,''' and again in 1877,'' Coues referred to Synaptovrys 

 cooperi, a s})ecimen from Skagit valley. Washington, collected in 

 1859 by C. B. Kennerly, and one from Nulato, Alaska, collected 

 in 18B7 by William II. Dall. These specimens are still in the 

 U. S. National Museum, and through the courtesy of Mr. True 

 I have l)een enabled to compare them with his type of Mictomys 

 innultus, which they closely resemble. Botli belong to the suIj- 

 genus Mi.ctomys, but differ suiliciently from innultus and from 

 each otlier to warrant separation. They are here described under 

 the names truei and dalli. 



In September, 1895, Clark P. Streator collected, at ^^'rangel, 

 Alaska, still another member of the same group, which is here 

 named unrmyeli. 



Sainiiuiry. — The material now available shows that the genus 

 Sy IK (p to mi /s, instead of being monotypic, as until recently sup- 

 posed, comprises 2 well marked subgeneric groups — Symiptnmys 

 proper and 7l//c'to/;?.7/.s ; that Synaptomys proper inhal)its eastern 

 Canada and the northeastern United States from Minnesota to 

 New Brunswick and New England, and contains 4 fairl}^ Avell 

 defined forms ; that Micfoiiiys has a transcontinental distribution 

 from Labrador to Alaska, and contains at least 4 species. 



Synaptomys, like the other genera of lemmings, is a distinctly 

 boreal group. Of the two sul)genera, Mictomys is decidedlv the 

 more boreal, being strictly confined, in the east at least, to the 

 Hudsonian zone. The sul)genus Synaptomys pushes southward 

 to the northern edge of the Austrori}>arian zone, ))ut after it leaves 

 the Boreal zone it occurs only, so far as known, in cool s\vam])s. 



Genus SYNAPTOMYS liaird. 



Subgenus Siinnpfoimji^ Baird, 1857. 



Ini'eriui- molars with well defined closed enamel loops on outer side ; 



upper incisors very broad and heavy, with enamel face deep 



orange throughout; posterior end of palate without median 



azygos ridge or projection. 

 Subgenus Mictomys True, 1894. 



Inferior molars with no closed 



enamel loops on outer side ; 



upper incisors relatively 



narrow and weak, with en- 

 amel face pale yellow and 



])art on outer side of sulcus 



nearly white ; posterior end 



of palate with a strongly 



marked median azygos Fi*^- i.— Enamel pattern of lower molars, 

 ridge and projection. i. Synaptomys 2. M,clomys. 



