224 BULLETIN 79, UNITED STATES NATIONAL MUSEUM. 



*Microtus xanthognathus (Leach). 



1815.~Arvicola xanthognathxi Leach, Zool. Miscell., vol. 1, p. 60. 

 1885. Arvicola xanthognathus True, Proc. U. S. Nat. Mus., 



vol. 7 (1884), p. 597. 1885. 

 1896. M{icrotus\ xanthognathus Miller, North Amer. Fauna, 



No. 12, p. 66. July 23, 1896. 

 Type Locality. — Hudson Bay. 

 Kange. — Northwestern Canada and Alaska, from central Alberta 



north to the Arctic coast and west to central Alaska. 



*Microtus chrotorrhinus chrotorrhinus (Miller). 



1894. Arvicola chrotorrhinus Miller, Proc. Boston Soc. Nat. 

 Hist., vol. 26, p. 190. March 24, 1894. 



1896. Microtus chrotorrhinus Bangs, Proc. Biol. Soc. Washing- 

 ton, vol. 10, p. 49. March 9, 1896. 



Type Locality. — Head of Tuckerraan's Ravine, Mount Wash- 

 ington, Coos County, New Hampshire. Altitude, 5,300 feet. 



Range. — Mount Washington, the Catskills, central Quebec, and 

 northern New Brunswick; in the Hudsonian zone. 



Microtus chrotorrhinus ravus Bangs. 



1898. Microtus chrotorrhinus ravus Bangs, Proc. Biol. Soc. 



Washmgton, vol. 12, p. 188. November 16, 1898. 

 Type Locality. — Black Bay, Strait of Belle Isle, Labrador. 

 Range.— Known only from the type locality. 



Subgenus Aulacomys Rhoads. 



1894, Aulacomys Rhoads, Amer. Nat., vol. 28, p. 182. Type, 

 Aulacomys arvicoloides Rhoads. 



*Microtus richardsoni richardsoni (DeKay). 



1842, Arvicola richardsoni DeKay, Zool. New York, mamm., 



p. 91. 

 1894. Aulacomys richardsoni Rhoads, Proc. Acad. Nat. Sci. 



Philadelphia, p. 288. October 23, 1894. 



1897. [Microtus] richardsoni Trouessart, Catal. Mamm. viv. 

 foss., p. 565. 



Type Locality. — "Near the foot of the Rocky Mountains." 



According to Bailey (North Amer. Fauna, No. 17, p. 60, June 6, 1900), 

 the type was collected by Drummond in the vicinity of Jasper House, Al- 

 berta, Canada. 



Range. — The typical form is kno^vn only fi'om the vicinity of 

 Jasper House and Henry House, Alberta, Canada. To the 

 south it apparently grades into Tnacrojpus in the Rocky Moun- 

 tains and arvicoloides in the Cascades. 



