_Range._--Known from the Mogollon, San Mateo, and Magdalena mountains of western New Mexico. _Remarks._--Bailey (Proc. Biol. Soc. Washington, 26:133, May 21, 1913) described this animal as a species and gave as general characteristics: "Size slightly larger than _E._ [= _Clethrionomys gapperi_] _galei_; colors duller, grayer and less buffy; skull and dentition heavier." He further characterized the skull as: "Larger, heavier and conspicuously more ridged than in _galei_; bullae large and especially deep; dentition heavy throughout." The type of _C. limitis_, as judged from the measurements given by Bailey (_loc. cit._), is an exceptionally old male. Our comparison of six adult topotypes with a series of _C. g. galei_ from Wyoming (18 adults from 3 mi. SSE Browns Peak, 10,000 ft., Albany County, in Univ. Kansas Mus. Nat. Hist.) and with three near-topotypes of _C. g. galei_ (3 mi. S Ward, 9000 ft., Boulder County, Colorado, in Univ. Kansas Mus. Nat. Hist.) revealed that most of the differences noted by Bailey (_loc. cit._) are not evident when individuals of comparable ages are examined. Some specimens of _C. g. galei_ exceed _C. limitis_ in ridging of the skull and size of the teeth although conspicuous ridges and large teeth are supposedly distinctive of _C. limitis_. The bullae, although averaging larger in _C. limitis_, can be matched in size by those of specimens of _C. g. galei_ from Wyoming. The differences evident between _C. limitis_ and _C. g. galei_ are of the kind and degree that serve to separate subspecies in the species _Clethrionomys gapperi_ and, although actual evidence of intergradation is lacking, we think that the relationships of _limitis_ are better expressed by arranging it as a subspecies of _C. gapperi_ than by retaining it as a full species. _Specimens examined._--Total, 7, all in the Biological Surveys Collection, distributed as follows: +New Mexico+: _Catron County_: Willow Creek, 8500 ft., Mogollon Mountains, 4. _Socorro County_: San Mateo Peak, 10,000 ft., San Mateo Mountains, 2; Copper Canyon, 9000 ft., Magdalena Mountains, 1. +Clethrionomys gapperi arizonensis+, new subspecies _Type._--Female, adult, skin and skull; No. 158401, Biological Surveys Collection, United States National Museum; from Little Colorado River, 8300 ft., White Mountains, Apache County, Arizona; obtained September 12, 1908, by C. Birdseye, original number 152. _Range._--Known only from the White Mountains of eastern Arizona. _Diagnosis._--Dorsal stripe near Chestnut, with an underwash of between Tawny and Russet, and a mixture of black-tipped hairs, resulting in an overall effect of near Chestnut. Skull wide across zygomatic arches and narrow across mastoids; rostrum narrow and posterior border of palate straight.