This subspecies of the Cascades of Oregon and _Thomomys monticola nasicus_ of the territory immediately to the east of the Cascades, in the same state, were originally described (Merriam, Proc. Biol. Soc. Washington, 11:214 and 216, respectively, July 15, 1897) and redescribed (Bailey, N. Amer. Fauna, 39:123 and 125, respectively, November 15, 1915) as distinguished from each other by paler color, smaller tympanic bullae and longer nasals in _T. m. nasicus_. The holotypes do differ in these respects. The assigned (by Bailey, _loc. cit._) specimens indicate that the opposite condition obtains with respect to the size of bullae; that is to say, the bullae are smaller in _T. m. mazama_. In these referred specimens from Oregon the nasals are actually and relatively longer in _T. m. nasicus_, which averages paler (less black and more red). Certain specimens of the two subspecies that are comparable as to sex, age and season, are indistinguishable in color. This is the background against which Bailey (_op. cit._:125), contrary to his statement of geographic ranges (_op. cit._:123, 125) and map (_op. cit._:fig. 5, p. 23), assigned, in his list of specimens examined, two specimens ([** Male] ad. 79817 and [** Female] ad. 79818 BS) from Pengra, west of the Cascades, to the subspecies _T. m. nasicus_. In the specimens from Pengra the bullae are angular as in referred specimens of _nasicus_ (unlike those of the holotype), the rostra are intermediate in length between those of the two subspecies concerned, and the color is light as in _T. m. nasicus_ but can be matched by that of certain specimens of _T. m. mazama_, for example by that of No. 79821 BS from Diamond Lake, Oregon. Consequently, on morphological grounds, the two specimens from Pengra can be assigned to _T. m. mazama_ almost as well as to _T. m. nasicus_. Having regard for the geographic relations, we assign them to _T. m. mazama_. In making this tentative identification we are aware that the acquisition of more nearly adequate material from Oregon, and critical study of such material, may bring a subspecific arrangement of the populations of _Thomomys monticola_ different from the current one. ~Thomomys talpoides bullatus~ Bailey Bailey (N. Amer. Fauna, 39:101, November 15, 1915) identified as _Thomomys talpoides clusius_ two specimens (66465 and 66523 BS) from Pass (= Parkman) and one specimen (66464 BS) from Dayton, in Wyoming. We have examined these specimens and find that they lack the broad braincase and narrow nasals of _clusius_ and in these and in other features the three specimens resemble _T. t. caryi_ and _T. t. bullatus_ more than they resemble any other named kinds. Although structurally, and in color, intermediate between the two subspecies named immediately above, the specimens show greater resemblance (large size and narrow braincase) to the latter and are referred by us to _Thomomys talpoides bullatus_. ~Thomomys talpoides clusius~ Coues