Intergradation with _invicta_ is shown by specimens from southwestern Montana. Where the margins of the geographic ranges of _invicta_ and _muricus_ approach one another elsewhere, low-lying territory, zonally unsuited to the existence of the species, occurs along the Snake and Columbia rivers, and precludes any chance of intergradation except around the head of the Snake River Plains. Two specimens, here referred to _muricus_, from Siskiyou County, California, in both color and cranial characters, are intergrades with _streatori_ and might be referred with almost equal propriety to _streatori_.
_Specimens examined._--Total number, 52, arranged alphabetically by states, then by counties from north to south within each state. Unless otherwise indicated, specimens are in the Museum of Vertebrate Zoölogy, University of California at Berkeley.
=California.= _Siskiyou County_: head of Rush Creek, 6400 ft., 1; Castle Lake, 5434 ft., 1. _Tehama County_: 2 mi. W Black Butte, 6800 ft., 1. _Placer County_: ridge W of Tahoe Pines, Lake Tahoe, 1; Blackwood Creek, 6250 ft., near Tahoe Pines, 1. _El Dorado County_: Fallen Leaf Lake, 6500 ft., 1[33]; Echo, 1[75]. _Tuolumne County_: Ten Lakes, 9200 ft., Yosemite Park, 1. _Mariposa County_: Vogelsang Lake, 10350 ft., Yosemite Park, 1. _Mono County_: Mammoth, 1[59].
=Colorado.= _Rio Blanco County_: Marvine, 1. _Boulder County_: Camp Albion, 10600 ft., 1[60]; Boulder, 1[91]. _Denver County_: Denver, 1[57]. _Park County_: Jefferson, 1[57]. _Gunnison County_: near Placita in Gunnison County, 1[26]; Crested Butte, 9000 ft., 3 (1[91], 2[19]). _El Paso County_: Turkey Creek, SW Colorado Springs, 6000 ft., 1[19]. _Chaffee County_: Arbourville, 1[91]; Hancock, 1. _Montrose County_: Coventry, 6800 ft., 1[19]. _San Juan County_: Silverton, 1[91]; in San Juan County above timberline, 1[87].
=Idaho.= _Bannock County_: West Fork of Rapid Creek, 9-1/2 mi. E Pocatello, 1.
=Montana.= _Meagher County_: Camas Creek, Big Belt Mts., 4 mi. S Ft. Logan, 1[91]. _Beaverhead County_: Donovan, 1[91]. _County_ in question: Yellowstone Park, 1[75].
=Nevada.= _Humboldt County_: Alder Creek, 6000 ft., Pine Forest Mts., 1. _Ormsby County_: 1/2 mi. S Marlette Lake, 8150 ft., 1. _Nye County_: South Twin River, Toyabe Mts., 1[91]. _White Pine County_: Baker Creek (8500 ft., 8675 ft., 11100 ft.), 3.