Specimens of _E. umbrinus montanus_ from north-central Colorado have, in the past (Howell 1929:82), been referred to _E. quadrivittatus quadrivittatus_. In many features these two kinds of chipmunks resemble each other closely; their bacula, nevertheless, differ markedly (compare figs. 8-9 with 17-18). _Specimens examined_: 25. _E. umbrinus umbrinus_: Wyoming: _Uinta Co._: 10 mi. S and 1 mi. W Robertson, 8,700 ft, 1. Utah: _Uintah Co._: Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., 12. _E. u. adsitus_: Utah: _Beaver Co._: Britts Meadow, Beaver Range Mountains, 8,500 ft, 1 (BS). _Wayne Co._: Donkey Lake, Boulder Mountain, 10,000 ft., 1 (UU). _Garfield Co._: Wildcat R. S., Boulder Mountain, 8,700 ft., 1 (UU). _E. u. sedulus_: Utah: _Garfield Co._: Mount Ellen, Henry Mountains, 1 (BS). _E. u. inyoensis_: California: _Tulare Co._: Mount Whitney, head of Big Cottonwood Creek, 2 (BS). Nevada: _Elko Co._: W side Ruby Lake, 3 mi. N Elko County Line, 1. _E. u. nevadensis_: Nevada: _Clark Co._: Sheep Mountains, 1 (MM). _E. u. fremonti_: Wyoming: _Sublette Co._: 31 mi. N Pinedale, 8,025 ft., 1; 19 mi. W and 2 mi. S Big Piney, 1. _E. u. montanus_: Colorado: _Boulder Co._: 3 mi. S Ward, 9,000 ft., 1; 1/2 mi. E and 3 mi. S Ward, 9,400 ft., 1. #Eutamias palmeri# Merriam Figures 17-18 General tone of upper parts grayish tawny; ocular stripe pale; skull, rostrum, nasals, and upper incisors shorter than in _E. umbrinus_. Baculum: Indistinguishable from that of _E. umbrinus_. This supports the opinion of previous students that _E. palmeri_ is a close relative of _E. umbrinus_ which occurs immediately to the north and east. Intergradation does not occur between these two species, for, low-lying terrain, inhospitable to chipmunks, isolates _E. palmeri_ from its relatives. (Verbal information from E. R. Hall.) _Specimen examined_: One from Charleston Peak, 8,000 ft., Clear Creek Co., Nevada. #Eutamias bulleri# (J. A. Allen) Figure 19 General tone of upper parts dark; dorsal dark stripes conspicuous and black; size large; skull large. Baculum: Shaft thick; keel high, 1/2 of length of tip; keel long, 1/2 of length of tip; tip 40 to 48 per cent of length of shaft; angle formed by tip and shaft 100°; base markedly widened; shaft of medium length, 3.30 mm. For comparisons with all other species of chipmunks of western North America, see the accounts of those species. The large size of the keel of the baculum in this species is distinctive among chipmunks of western North America. _Specimens examined_: 2. _E. bulleri bulleri_: Zacatecas: Sierra de Valparaiso, 2 (NM). [Illustration: FIGS. 1-19. Lateral view of right side, unless otherwise indicated, of the baculum in each of the species of chipmunks (subgenus _Neotamias_) of western North America: