_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. _Zapus pacificus_ Merriam, Proc. Biol. Soc. Washington, 11:104, April 26, 1897 (part--the part from Point Reyes, Marin County, California).