_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: