_Remarks._--Merriam (1897a:103) named this jumping mouse as a full species, mentioning that the skull is similar in size and characters to that of _Zapus hudsonius_ but that externally these animals differed in coloration and length of the tail. Hall (1934:377) treated _Z. tenellus_ as a subspecies of _Z. hudsonius_. He observed that the difference between _Z. tenellus_, _Z. h. alascensis_, and _Z. h. hudsonius_ was of the same degree, and, even though intergrading material was not known to him, he considered _tenellus_ only subspecifically distinct from _Z. hudsonius_. Hall (_loc. cit._) tentatively referred to _Z. h. tenellus_ specimens from Indianpoint Lake, 15 mi. NE Barkerville, Cottonwood P. O., and Hazelton, British Columbia. I have seen and compared with the type of _Z. tenellus_ all specimens examined by Hall and agree with him that they are best referred to _Z. h. tenellus_. Since 1934, several additional localities in British Columbia have yielded specimens. Those from Minaker River and Fort St. John are intermediate in dorsal coloration and in size and shape of the auditory bullae between _Zapus hudsonius hudsonius_ and _Z. h. tenellus_ but in all other characters are most nearly like _Z. h. tenellus_ to which they are here assigned. These intergrades constitute additional evidence that _Z. tenellus_ and _Z. hudsonius_ are only subspecies of a single species. _Specimens examined._--Total, 17, all from British Columbia, distributed as follows: east side Minaker River, 1 mi. W Trutch, 1; Hazelton, 959 ft., 2 (MVZ); 5 mi. W and 3 mi. N Fort St. John, 1; _Indianpoint Lake, 15 mi. NE Barkerville_, 5 (MVZ); Cottonwood P. O., 3 (MVZ); S end Swan Lake, Vernon, 1200 ft., 2 (MVZ); Kamloops, 3 (USBS). _Marginal records._--British Columbia.--E side Minaker River, 1 mi. W Trutch; 5 mi. W and 3 mi. N Fort St. John; S end Swan Lake, Vernon, 1200 ft.; Kamloops; Hazelton, 959 ft. TABLE 5.--Cranial Measurements (in Millimeters) of Zapus. Column headings: Col. A: Number examined, [M][M] plus [F][F] Col. B: Breadth of braincase Col. C: Condylobasal length Col. D: Interorbital breadth Col. E: Mastoidal breadth Col. F: Length of maxillary tooth-row Col. G: Occipitonasal length Col. H: Palatal length Col. I: Zygomatic breadth Col. J: Zygomatic length