In the Teton Range and in Yellowstone National Park these garter snakes occur in headwater streams up to the Continental Divide. KU 27956 from Two Ocean Lake 3-1/2 miles northeast of Moran, Teton County, Wyoming, agrees in its characters with _fitchi_, having the red lateral marks small and inconspicuous, discernible only on the anterior half of the body. The dorsolateral area is dark, almost black. The ventrals lack dark markings. In Utah, populations of _sirtalis_ occur in the drainages of the Bear, Weber and Sevier rivers and other smaller streams of the western half of the state. Obviously the species invaded Utah from the north, probably at a time when Lake Bonneville, the predecessor of the present Great Salt Lake, drained into the Snake River of Idaho. Van Denburgh and Slevin (1918:190) separated from their western "_concinnus_" and "_infernalis_" and allocated to _parietalis_ the populations of Utah and southeastern Idaho, but presumably these authors were not familiar with typical _parietalis_ of the Mid-west. Subsequent authors (Wright and Wright, 1957:834; Stebbins, 1954:505; Conant, 1958:328) have followed this arrangement. A re-examination of specimens from Utah, including living individuals collected at Bear Lake in the summer of 1959, indicates that they should be assigned to _fitchi_ rather than to _parietalis_. Likewise various specimens from the drainage basin of the Snake River in Idaho are predominantly _fitchi_ in the sum of their characters, although they differ from that subspecies in its most typical form and resemble _parietalis_ in some respects. KU 23133 from two miles east of Notus, Canyon County, Idaho, has the red crescents on the lower part of the sides (between scale rows six and seven) consistently developed on the anterior half of the body. KU 21873, a large female from Bannock County, Idaho, is exceptional in having small lateral black spots on the ventrals, resembling _parietalis_ most closely in this respect. Also, it has the red lateral crescents unusually well developed; the first three series are conspicuous, those of the fourth series are consistently developed, and those of the fifth series show occasionally.