For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, and _E. sonomae_, see the accounts of those species.
Bacula from skins labeled as _E. amoenus amoenus_ from, Lardo, Valley Co., Idaho (MM), Butte Co., Idaho (MM), and Boise National Forest, Idaho (BS), resemble the bacula of _E. umbrinus_, and critical study of other features of these specimens probably will show that they are _E. umbrinus_.
_E. amoenus amoenus_: Oregon: _Klamath Co._: Fort Klamath, 1 (MM). Idaho: _Valley Co._: Lardo, 1 (BS). _Butte Co._: Unspecified, 1 (MM). Boise National Forest, 1 (BS).
_E. a. ludibundus_: British Columbia: Moose Lake, 1 (NM).
_E. a. luteiventris_: Alberta: Banff, 2 (BS). Montana: _Flathead Co._: 1 mi. W and 2 mi. S Summit, 5,000 ft., 1. _Teton Co._: 17-1/8 mi. W and 6-1/2 mi. N Augusta, 5,100 ft., 2. _Missoula Co._: Unspecified, 1 (MM). Idaho: _Idaho Co._: 20 mi. S and 2 mi. E Grangeville, 2. _Fremont Co._: 7 mi. W West Yellowstone, 7,000 ft., 5; 9 mi. SW West Yellowstone, 8,500 ft., 1. Wyoming: _Teton Co._: 2-1/2 mi. N and 3-1/2 mi. E Moran, 7,225 ft., 1.
_E. a. monoensis_: California: _Mono Co._: Leevining Creek, 1 (NM).
_E. a. vallicola_: Montana: _Ravalli Co._: Bass Creek, 3-1/2 mi. NW Stevensville, 3,750 ft., 2.
General tone of upper parts smoky gray; dorsal stripes indistinct or obsolete; skull large.
Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 29 to 40 per cent of length of shaft; angle formed by tip and shaft 140°; distal 1/2 of shaft slightly compressed laterally; shaft short to medium, 2.64 to 3.69 mm.
Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not widened, shaft thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum usually shorter; from _E. merriami_, in shaft markedly shorter, base not incised dorsally, tip proportionally longer.
For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, and _E. amoenus_, see the accounts of those species.
_E. dorsalis dorsalis_: Arizona: _Yavapai Co._: 3 mi. N Ft. Whipple, 5,000 ft., 1 (BS). _Gila Co._: Carr's Ranch, Sierra Ancha Mountains, 1 (BS). _Pima Co._: Unspecified, 1 (MM). New Mexico: _Valencia Co._: Mount Taylor, 1 (MM); 1 mi. N Cebolleta, 1 (MM). _Socorro Co._: San Mateo Mountains, 1 (BS). _Chihuahua_: Sierra Madre, near Guadalupe y Calvo, 3 (BS).