Specimens from the eastern part of the range of _P. f. fasciatus_ are somewhat smaller and slightly darker than topotypes from Buford, North Dakota. Specimens from 9 mi. SE Bainville, Johnson Lake and 3 mi. S Medicine Lake, Montana, and from Crosby, North Dakota, are also paler than those from farther east. At the southern limit of the range of the subspecies, specimens from the Rosebud Agency and Minichaduza River, South Dakota, approach _olivaceogriseus_ in pale dorsal coloration. _Specimens examined._--Total number, 83, as follows: MANITOBA: Aweme, 3 (USBS 2, NMC 1). Junction of Antler and Souris rivers, 1 (NMC). Oak Lake, 2 (NMC). MONTANA: _Roosevelt County_: 9 mi. SE Bainville, 4 (MZ); Johnson Lake, 2 (USBS). _Sheridan County_: 3 mi. S Medicine Lake, 1880 ft., 1 (KU). NEBRASKA: _Cherry County_: Ft. Niobrara Game Reserve, 1 (NSM); Sparks, 1 (MZ); Valentine, 2 (UNDZ). NORTH DAKOTA: _Benson County_: 2 mi. W Fort Totten, 1400 ft., 3 (KU). _Bottineau County_: Bottineau, 1 (CNHM). _Burleigh County_: 9 mi. E Bismark, 7 (MZ). _Dickey County_: Oakes, 2 (CNHM 1, USBS 1). _Divide County_: Crosby, 1 (USBS). _Kidder County_: Dawson, 1 (USBS); 6 mi. W Steele, 6 (MZ). _McHenry County_: 1/2 mi. E Upham, 1 (USBS). _Morton County_: 12 mi. W Mandan, 2 (MZ). _Oliver County_: Ft. Clark, 8 (USBS). _Sargent County_: 7-2/10 mi. E, 1-2/10 mi. S Oakes, 1200 ft., 1 (KU). _Sioux County_: Cannon Ball, 6 (USBS). _Stark County_: 1 mi. S Dickinson, 1 (MZ); 9 mi. W Dickinson, 3 (MZ); 2 mi. W Taylor, 4 (MZ). _Stutsman County_: 7 mi. N Jamestown, 1 (MZ); 14 mi. W Jamestown, 1 (MZ). _Wells County_: Bowdon, 1 (USBS). _Williams County_: Buford, 9 (USBS). SOUTH DAKOTA: _Todd County_: Minichaduza River, 2 (USBS); Rosebud Agency, 1 (USBS). _Tripp County_: Colome, 3 (MZ). _Walworth County_: Swan Creek, 13 mi. S Shelby, 1600 ft., 1 (KU). =Perognathus fasciatus olivaceogriseus= Swenk _Perognathus flavescens olivaceogriseus_ Swenk, Missouri Valley Fauna, 3:6, June 5, 1940, type from [Little Bordeaux Creek, sec. 14, T. 33 N, R. 48 W, 3 mi. E] Chadron, Dawes County, Nebraska. _Geographic distribution._--Southeastern Alberta, southeast to eastern Wyoming and adjacent parts of South Dakota and Nebraska.