226 BULLETIN 79, UNITED STATES NATIONAL MUSEUM. 



t*Microtus haydenii (Baird). 



1857. Arvicola (Pedomys) haydenii Baird, Mamm. N. Amer., 

 p. 543. 



1894. Arvicola (Pedomys) Tiaydenii Allen, Bull. Amer. Mus. 

 Nat. Hist., vol. 6, p. 328. November 7, 1894. 



1895. Microtus {Pedomys) Tiaydenii Allen, Bull. Amer. Mus. 

 Nat. Hist., vol. 7, p. 267. August 21, 1895. 



Type Locality. — Fort Pierre, Stanley County, South Dakota. 

 Range. — Plains region or western South Dakota, Nebraska, and 



Kansas, eastern Colorado and Wyoming, and southern Montana, 



in transition zone. 



t*Microtus minor (Merriam). 



1888. Arvicola austerus minor Merriam, Amer. Nat., vol. 22, 



p. 600. July, 1888. 

 1900. Microtus minor Bailey, North Amer. Fauna, No. 17, p. 75. 



June 6, 1900. 

 Type Locality. — Bottineau, at base of Turtle Mountains, 



Bottineau County, North Dakota. 

 Range. — Northern border of the Great Plains from northeastern 



North Dakota to Edmonton, Alberta, and southeastward to 



Minneapolis, Minnesota. 



Subgenus Orthriomys Merriam. 



1898. Orthriomys Merriam, Proc. Biol. Soc. Washington, vol. 12, 

 p. 106. April 30, 1898. Type, Microtus umbrosus Merriam. 



t*Microtus umbrosus Merriam. 



1898. Microtus umbrosus Merriam, Proc. Biol. Soc. Wash- 

 ington, vol. 12, p. 107. April 30, 1898. 



Type Locality. — ^Mount Zempoaltepec, State of Oaxaca, 

 Mexico. Altitude, 8,200 feet. 



Range. — Known only from the east slope of Mount Zempoal- 

 tepec, in the humid upper austral zone. 



Subgenus Herpetomys Merriam. 



1898. Herpetomys Merriam, Proc. Biol. Soc. Washington vol. 

 12, p. 107. April 30, 1898. Type, Microtus guatemalensis 

 Merriam. 

 t*Microtus guatemalensis Merriam. 



1898. Microtus guatemalensis Merriaiii, Proc. Biol. Soc. Wash- 

 ington, vol. 12, p. 108. April 30, 1898. 



Type Locality. — Todos Santos, State of Huehuetenango, 

 Guatemala. Altitude, 10,000 feet. 



Range. — Known only from the type locality. 



