1915. J 



THOMOMYS FUSCUS GEOUP. 



127 



Characters. — Size rather small ; feet slender ; ears small and pointed ; 

 color light brown J skull slender, with large bullae; dentition light; 

 mammae in 4 pairs, inguinal 2-2, pectoral 2-2, 



Color. — Summer pelage: Upperparts light brownish or dull walnut- 

 brown, not so dark as in fossor nor so bright as in monticola or mazama; 

 ear patch black or blackish; nose plumbeous; underparts buffy; feet 

 and tail soiled whitish or buffy; tail usually gray above at base. 

 Winter pelage: SHghtly duller than summer. Young, paler than 

 adults. 



Slcull. — Light and slender with short rostrum and anteriorly con- 

 verging lateral ridges; interparietal wide and oval; nasals short and 

 truncate posteriorly, reaching nearly to tips of premaxillse; bullae 

 full and rounded; pterygoids long and narrowly V-shaped; skulls 

 of males and females very similar. Dentition light; upper incisors 

 abruptly decurved and distinctly grooved. 



Measurements. — Average of 3 topotypes ( c? ad): Total length, 

 203; tail vertebrae, 70; hind foot, 27. Average of 5 adult females: 

 205, 70, 27. Slull (of type, 9 ad.): Basal length, 33; nasals, 12.4; 

 zygomatic breadth, 20; mastoid breadth, 17; interorbital breadth, 

 6; alveolar length of upper molar series, 7. 



RemarJcs. — This form is fairly typical in central Idaho, western 

 Montana, and in the Blue Mountain region of Oregon. In northern 

 Idaho, eastern Washington, and southern British Columbia it becomes 

 noticeably darker, but retains more nearly the skull characters of 

 fuscus. West of the Columbia River it varies greatly with almost 

 every locality, but these local forms can be placed under fuscus better 

 than with quadratus or myops, both of which they suggest. 

 Specimens examined. — Total number, 373, as foUows: 

 British. Columbia: Ashcroft, 1; Cascade, 6; Ducks, 5; Glacier, 1; Kamloops, 2; 

 Midway, 6; Monashee Ridge (Gold Range, at 4,000 feet altitude, 5; at 3,620 

 feet, 4), 9; Myers Creek, 1; Nelson, .9; Okanogan, 10; Pend Oreille River, 

 11; Salmon River, 2; Shuswap, 20; Skagit Valley, 1; Trail, 1; Wards 

 Ferry, 1. 



Idaho: Ashton, 2; Big Lost River (head), 2; Blackfoot (west of river), 1; Blue 

 Lake, 12; Coeur d'Alene, 4; Freedom (near mouth of South Fork Salmon 

 River), 1; Hoodoo Valley, 1; Lemhi Indian Agency, 2; Lerdo, 1; Lost River 

 Mountains, 5; Midvale, 7; Mission, 1; Mount Carlton, 3; New Meadows, 3; 

 Salmon River Mountains, 11; Sawtooth Lake, 3; Seven Devils Mountains, 2; 

 South Fork Ranch, 1; Teton Canyon, 1; Van Wyck, 1. 



Montana: Beartooth Mountains, 3; Benton (west of), 1; Corvallis, 2; Flathead 

 Lake. 4; Fort Ellis, 2; Little Bitterroot Creek, 1; Lo Lo, 1; Midvale, 2; Ross 

 Fork, 1; St. Marys Lake, 3; Stevensville, 2; Summit (west of Blackfoot 

 Station), 6; Thompson Falls, 8; Tobacco Plains, 10. 



Oregon: Antelope, 2; Anthony, 14; Bingham Prairie, 1; Blue Mountains (10 miles 

 north of Harney), 1; Elgin, 1; Huntington, 1; Wallowa Mountains, 8. 



