420 BULLETIN 128, UNITED STATES NATIONAL MUSEUM. 



t*Microtus ludovicianus Bailey. 



1900. Microtus ludovicianus Bailey, North Amer. Fauna, No. 17, 



p. 74. June 6, 1900. 

 Type Locality. — Iowa, Calcasieu Parish, Louisiana. 

 Range. — Coast prairie of southwestern Louisiana, in lower 



austral zone. 



t*Microtis haydenii (Baird). 



1857. Arvicola {Pedomys) liaydenii Baird, Mamm. N. Amer., 

 p. 543. 



1894. Arvicola {Pedomys) liaydenii Allen, Bull. Amer. Mus. 

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



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

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



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



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

 Kansas, eastern Colorado and Wyoming, and southern Mon- 

 tana, in Transition zone. 



t*Microtus mLUor (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 umhrosus 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, Oaxaca, Mexico. Alti- 

 tude, 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. 



