_Marginal records._--Oregon: Prospect. Nevada: 3 mi. S Mt. Rose, 8500 ft.; 1/2 mi. E Zephyr Cove, Lake Tahoe, 6400 ft. California: Mono Lake P. O., 6500 ft.; 2 mi. E Kern Peak, 9300 ft., Sierra Nevada Mts.; Rich Gulch, 3850 ft., 11 mi. W and 8 mi. N Quincy; Warner Creek, 8000 ft., Lassen Peak; 2 mi. S Yolla Bolly Mtn.; 8 mi. NE Hyampon, 2900 ft.; Siskiyou Mts., 6000 ft.; Poker Flat, 5000 ft., 12 mi. NW Happy Camp. =Zapus princeps princeps= J. A. Allen _Zapus princeps_ J. A. Allen, Bull. Amer. Mus. Nat. Hist., 5:71-72, April 28, 1893; Preble, N. Amer. Fauna, 15:23, August 8, 1899. _Type._--Female, adult, skin and skull; No. 5260/4140, Amer. Mus. Nat. Hist.; Florida, La Plata County, Colorado; obtained on June 27, 1892, by Charles P. Rowley. _Range._--Sierra Madre, Medicine Bow, Laramie, and Big Horn mountains of Wyoming southward through Colorado into the Taos and San Juan mountains in northern New Mexico. See fig. 46. Zonal range: Transition, Canadian and Hudsonian. _Description._--Size, medium; back dark usually with broad mid-dorsal band of black mixed with Warm Buff or Ochraceous-Buff; sides light (Warm Buff) but varying to Ochraceous-Buff, always with admixture of black hair; lateral line distinct and broad, varying from Light Ochraceous-Buff to Ochraceous-Buff; ventral surface white to base of hairs, frequently suffused with Ochraceous-Buff; tail indistinctly bicolored, tan to grayish-white below and pale brown above; hind feet grayish-white above; ears edged with white or yellowish-white; skull medium; large medial projection on inferior ramus of zygomatic process of maxillary; palate moderately long; postpalatal notch usually broadly rounded and posterior to posterior part of last molar; proximal part of inferior ramus of zygomatic process of maxillary broad; pterygoid fossae broad; auditory bullae moderately inflated. _Comparisons._--From _Zapus princeps luteus_, _Z. p. princeps_ differs as follows: Total length, tail and hind foot longer; color darker, being less ochraceous; ears darker, edged with white or yellowish-white instead of Ochraceous-Buff; lateral line more distinct; skull larger, except least interorbital breadth which is smaller; auditory bullae larger, more inflated; pterygoid fossae larger; incisive foramina broader, longer, and posteriorly more truncate; nasals broader, tapering less distally.