As judged by the two skulls of subadult males from the Barkerville region, individuals of this race attain larger size than do those of _longicauda_. On the basis of larger size than either _longicauda_ or _nevadensis_, the specimens from the Rocky Mountains of Montana and two from northern Wyoming are referred to this race. The short, wide, flat, tympanic bullae, relatively great mastoidal breadth, and some other features of the specimen from Donovan, Montana, point toward _oribasus_, whereas nearly as many more cranial features, in this instance mainly differences in size, are indicative of _nevadensis_ to which race the specimen might almost equally well be referred. Another male from Darby, in the Bitterroot Valley of Montana, has a slightly longer hind foot than those from Florence, but a female from Hamilton, agrees more nearly with _nevadensis_. The average of all the specimens from the Bitterroot Valley is a little nearer _oribasus_. Four skulls from Buffalo, Wyoming, here referred to _nevadensis_ show approach to _oribasus_ in size of skull. The specimens from Big Snowy Mountains, and the Highwood Mountains of Montana are too young clearly to show size of the adult skull, but are distinctly darker colored than _longicauda_ of the plains country proper. Of two subadult females from Tacy, Montana, the color of the one in summer pelage is distinctly nearer that of _oribasus_ and _nevadensis_ than it is to that of _longicauda_ to which some approach in color might be expected. The reduced size of both of the specimens is further suggestive of _nevadensis_ and it may be that adult specimens from these more eastern mountainous areas in Montana will show that _nevadensis_ is the name proper to apply to animals of this region. Intergradation with _nevadensis_ is suggested by specimens collected from along the upper reaches of Okanagan Lake, British Columbia, by Major Allan Brooks and Mr. J. A. Munro and by a series of skulls from Ione, Pend Orielle County, Washington, lent me by Mr. Walter Dalquest. At each place, the average of all specimens is nearest to that of _nevadensis_. Specimens from near Waterton Lake show several steps in the transition from the light-colored _longicauda_ type of coloration to the darker coloration characterizing _oribasus_. One taken here, at a time when the body of water referred to seems to have been known as Chief Mountain Lake, is barely dark enough to be placed with _oribasus_. Two other specimens from across the Canadian Border labeled as "Waterton Lake Park" are slightly lighter colored above, and on this account are placed with _longicauda_.