Type.—Female, adult, skin and skull; No. 79863, U. S. Nat. Mus., Biol. Surv. Coll.; Crater Lake, Klamath County, Oregon; obtained on August 19, 1896, by Edward A. Preble, original No. 1388.

Range.—From Crater Lake, Klamath County, Oregon, northward along the Cascade Range into Hood River County, Oregon. Zonal range: Transition and Canadian.

Description.—Size medium; back near Ochraceous-Buff with admixture of black hair, resulting in a grizzled, broad, dorsal band; sides lighter than back, from near Ochraceous-Buff to near Pinkish-Cinnamon, and lined with black hair; lateral line distinct; underparts usually pure white, sometimes with slight suffusion of ochraceous on lower throat and upper chest; tail bicolored, brown above and yellowish-white below; ears dark, sometimes flecked with ochraceous, edged with yellowish-white; feet grayish-white above; braincase relatively narrow; zygomata relatively short; condylobasal length short; mastoid region relatively narrow; palatal bridge short; auditory bullae large; frontal region inflated; pterygoid fossae relatively narrow.

Comparison.—From Zapus trinotatus trinotatus, Z. t. montanus differs as follows: Size averaging smaller; sides more ochraceous, fewer black hairs; upper parts duller; skull smaller; zygomatic arch shorter, braincase relatively narrower; frontal region more inflated; pterygoid fossae relatively narrower; zygomata narrower.

Remarks.—The systematic status of Z. t. montanus has been in doubt. Several workers, for example, Howell (1920:227) and Preble (1899:28), considered it to be a species, and others (Merriam, 1897a:104, Bailey, 1936:234) considered it to be a subspecies of Z. trinotatus. Z. montanus is here considered to be a subspecies of Z. trinotatus, because of the agreement of the two in size and shape of the baculum, diameter and pigment pattern of the hair, and the over-all proportions of the skull. In addition, animals from intermediate geographic areas are available and show actual intergradation.

Intergradation has been noted in specimens from North Santiam River, 3400 ft., Oregon. In color, in length of incisive foramina, in breadth of braincase, and in width of zygomata these specimens are intermediate between Zapus trinotatus montanus and Z. t. trinotatus, but in the sum-total of characters they are referable to the former. Specimens from Lost Creek R. S., 10 mi. SE McKenzie Bridge, are intermediate in color between Z. t. trinotatus and Z. t. montanus; they are referable to Z. t. montanus. The animals available from Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood and the one from Mt. Hood, in color, in length of incisive foramina, and in mastoid width, closely approach Z. t. trinotatus from Skamania County, Washington, but in the sum-total of characters are nearest Z. t. montanus and are here referred to montanus.

Specimens examined.—Total, 35, all from Oregon, distributed as follows: Deschutes County: Tumalo Creek, 15 mi. W Bend, 6100 ft., 3 (MVZ). Douglas Co.: Diamond Lake, 1 (USBS). Hood River Co.: Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood, 10 (MVZ); Mt. Hood, 1 (USBS). Klamath Co.: Crater Lake, 3 (MVZ); 1/2 mi. N Government Camp, 6700 ft., Munson Valley, Crater Lake Nat’l Park, 2 (MVZ); east slope Cascade Divide, 6400 ft., Crater Lake Nat’l Park, 2; Anna Creek, Mt. Mazama, 6000 ft., 2 (USBS). Lane Co.: Lost Creek R. S., 10 mi. SE McKenzie Bridge, 6 (USBS); Three Sisters, Alder Springs, 4300 ft., 2 (USBS). Linn County: North Santiam River, 3400 ft., 3 (MVZ).

Marginal records.—Oregon: Brooks Meadow, 4300 ft., 9 mi. ENE Mt. Hood; Tumalo Creek, 15 mi. W Bend, 6100 ft.; Anna Creek, Mt. Mazama, 6000 ft.; east slope Cascade Divide, 6400 ft., Crater Lake Nat’l Park; Diamond Lake; North Santiam River, 3400 ft.

Zapus trinotatus orarius Preble

Zapus orarius Preble, N. Amer. Fauna, 15:29, August 8, 1899.