in: General tone of upper parts darker; braincase
significantly narrower; baculum shorter and markedly wider at
base.

From _E. u. umbrinus_, the subspecies from the Uinta and
northern Wasatch Mountains, _E. u. montanus_ differs in:
General tone of upper parts brighter (less tawny); sides more
tawny; skull slightly larger.

From _E. u. sedulus_, the subspecies from the Henry Mountains
of Utah, _E. u. montanus_ differs in: Sides darker; general
tone of upper parts darker.

From _E. u. fremonti_, the subspecies from the mountains of
western and northwestern Wyoming, _E. u. montanus_ differs
in: General tone of upper parts lighter; hairs around
outermost edge of tail tawnier.

_Remarks._--Howell (1929:83) stated that the specimens of _E.
quadrivittatus quadrivittatus_ (= _E. umbrinus montanus_) from Estes
Park, Long's Peak, and Gold Hill, all in Colorado, "average somewhat
darker on the back and sides than typical _quadrivittatus_; the light
dorsal stripes are also somewhat duller and the dark stripes less
blackish, thus showing an approach to the characters of _umbrinus_."
Now there are more specimens of _E. u. montanus_ from the mountains of
north-central Colorado than were available to Howell. He was not aware
of the striking difference between the bacula of _E. quadrivittatus_
and _E. umbrinus_, and the constancy of this difference between all
the subspecies of one species and those of the other.

Although the geographic range of _E. u. umbrinus_ is closer to the
ranges of _E. u. fremonti_ and _E. u. montanus_ than to the geographic
range of _E. u. adsitus_, _E. u. umbrinus_ seems to be more closely
related to _E. u. adsitus_ than to _E. u. fremonti_ or _E. u.
montanus_. This observation may be explained by the presence of
continuous habitat for _E. umbrinus_ between the ranges of _E. u.
umbrinus_ and _E. u. adsitus_, whereas _E. u. fremonti_ and _E. u.
montanus_ are each separated from _E. u. umbrinus_ by areas unsuitable
for occupancy by _E. umbrinus_. It must be noted, however, that no
actual intergrades between _E. u. umbrinus_ and _E. u. adsitus_ are
known.

_Specimens examined._--Total number, 36.

=Wyoming=: _Albany Co._: 3 mi. ESE Brown's Peak, 10,000 ft.,
2; 3-1/2 mi. S Wood's Landing, 1.

=Utah=: _Uintah Co._: PR Springs, 7,950 ft., 43 mi. S Ouray,
Uintah-Grand county line, 1 UU.

=Colorado=: _Jackson Co._: Mount Zirk