14 Proceedings of the Biological Society of Washington. 



Color. — Winter pelage: Median dorsal area hazel or mikado brown, not 

 sharply defined, shading into color of the sides, which are warm buff, 

 lightly shaded with fuscous; sides of face pale neutral gray; ears fuscous, 

 shaded with hazel; sides of nose pinkish buff; feet pinkish buff, shaded 

 with fuscous; tail above, tawny or mikado brown, bordered with black and 

 edged with warm buff; tail beneath, warm buff, mixed with neutral gray; 

 under parts white. Summer pelage: Upper parts warm buff, mixed with 

 fuscous, the head darker; sides of nose warm buff; ears ochraceous tawny, 

 shaded with fuscous; front feet ochraceous tawny; hind feet similar; the 

 toes buckthorn brown; tail above, russet, bordered with black and edged 

 with warm buff; tail beneath, mixed russet and neutral gray; under parts 

 white, faintly washed with pale pinkish buff. 



Measurements. — Average of 10 adults from Mouse River, North Dakota : 

 Total length, 333.4 (324-360); tail vertebrae, 132.9 (120-143); hind foot, 

 48.1 (46-49). Skull: Average of 10 adult males from same locality: 

 Greatest length, 47.6 (46.9-49) : zygomatic breadth, 26.6 (25-27.7); cranial 

 breadth, 20.5 (20-21.3); interorbital breadth, 13.5 (13-14.3); least post- 

 orbital breadth, 14.2 (13-15.1); length of nasals, 14.4 (12.9-15.7); maxillary 

 tooth row, 7.9 (7.6-8.2). Seven females average: Total length, 46.5; 

 zygomatic breadth, 26.6; cranial breadth, 20.1; the other measurements 

 are much as in the males. 



Remarks. — This race occupies a limited area in the Souris River Valley, 

 North Dakota, extending northward into the Turtle Mountains. It is the 

 palest of all the races of hudsonicus, the red on the back much reduced in 

 extent and intensity. In color it most resembles dakotensis, but is less 

 suffused with ochraceous. 



Specimens examined. — Total number, 31, from localities as follows: 

 North Dakota: Bottineau, 2; Max Lake, Turtle Mountains, 2;' Mouse 

 River, 10 miles east of Upham, and S. E. of Stillings Dam, 14; Towner, 7; 

 Turtle Mountains, 6.' 



United States Department of the Interior, Fish and Wildlife Service, Wash- 

 ington, D. C. 



2 Coll. Nat. Mus. Canada. 



s Two in American Mus. Nat. Hiet. 



