Zapus trinotatus pacificus, Bailey, N. Amer. Fauna, 55:233, August 29, 1936.
Zapus princeps alleni, Hall, Mammals of Nevada; Univ. California Press, Berkeley, California, 579, July 1, 1946.
Type.—Male, subadult, skin and skull, No. 80445, U. S. Nat. Mus. Biol. Surv. Coll.; Prospect, Rogue River Valley, Jackson Co., Oregon; obtained on August 29, 1896, by Edward A. Preble, original No. 1454.
Range.—Sierra Nevada Mt’s, from Kern Peak, Tulare County, California, northeastward to Mt. Rose, Washoe County, Nevada, then northwestward through the Trinity and Salmon mountains, California, to the upper Rogue River Valley, Oregon, thence southwestward to South Yolla Bolly Mt’n, Tehama County, California. See [fig. 46]. Zonal range: Transition, Canadian, and Hudsonian.
Description.—Size medium; color bright; back near Ochraceous-Buff with admixture of black hair forming dark dorsal band; sides bright Ochraceous-Buff with fine admixture of black hair; lateral line blending with color of sides or wanting or indistinct; ventral surface white; tail bicolored, grayish-brown above, yellowish-white below, in some specimens with white tip; feet grayish-white above; ears dark, edged with Ochraceous Buff; braincase relatively narrow; incisive foramina relatively short; pterygoid fossae usually broad; proximal part of inferior ramus of zygomatic process of maxillary broad; postpalatal notch usually broadly rounded; auditory bullae relatively small and flattened; nasals parallel sided; maxillary tooth-row short; interorbital region moderately broad.
Comparison.—From Zapus princeps oregonus, Z. p. pacificus differs in being brighter in all pigmented areas; more ochraceous and less yellow laterally; dorsally more ochraceous and less black; size averaging smaller; maxillary tooth-rows shorter; auditory bullae less inflated and smaller; interorbital region averaging narrower; palatal bridge averaging shorter; incisive foramina shorter and posteriorly narrower; nasals parallel rather than narrowed posteriorly.
Remarks.—Original describers considered both Z. pacificus and Z. alleni as specifically distinct from Z. trinotatus. Merriam (1897a:104) named Z. pacificus and gave the following diagnostic characters: short rostrum and nasals; small auditory bullae; basioccipital broad between bullae. Elliot (1898:212) named Z. alleni and ascribed to it the following diagnostic characters: cranium long and narrow; nasals same breadth for entire length; palate wide; pterygoid fossae wide posteriorly; auditory bullae small; basisphenoid and basioccipital wide; upper tooth-rows short. Preble (1899:27) considered Z. alleni to be a subspecies of the species Z. trinotatus, remarking that the skulls are similar to those of Z. trinotatus but smaller with much smaller bullae; in coloration the animals are lighter above and without fulvous below. Preble remarked that the skull of Z. alleni differs so greatly from that of Z. montanus that comparison was not required. Preble (op. cit.:30) treated Z. pacificus as a full species. Howell (1920:233) considered Z. pacificus and Z. alleni to be subspecies of Z. pacificus. Howell (loc. cit.) pointed out size, cranial, and color similarities between the two, and remarked that pacificus is clearly distinct from Z. montanus, its nearest geographic neighbor. Hall (1946:578) arranged Z. alleni as a subspecies of Z. princeps, although not on grounds wholly satisfactory to him because actual intergrades between alleni and neighboring races of princeps were not available.
I here consider Z. alleni to be synonymous with Z. pacificus; the latter is a subspecies of Z. princeps. Certain diagnostic characters, such as the shape and size of the os penis, the diameter and pigment pattern of the hair, the over-all proportions of the skull, and the size and shape of the teeth indicate that alleni and princeps belong to the same species, even though animals from intermediate geographic areas are not available to show actual intergradation.
The diagnostic characters referred to in the original description of Z. alleni, as given earlier in this account, agree with characters of specimens of Z. p. pacificus. Howell (1920:233) remarks that, in coloration and length of foot, typical alleni differs but slightly from pacificus. Howell (loc. cit.) noted, as I also have, that there are slight cranial differences in specimens from various parts of the range of Z. p. pacificus; these variations are somewhat clinal in nature, cranial dimensions showing a slight increase from south to north. The largest animals occur in western Tehama, Trinity, and Siskiyou counties, California. Samples from various localities in Jackson County, Oregon, are slightly smaller than these, but are larger than specimens from the southern Sierra Nevada.
Specimens examined.—Total, 264, distributed as follows: