ly in summer pelage), owing principally
to more suffusion of blackish middorsally; tail slightly shorter; ears
markedly shorter, rostrum shorter and relatively broader; occipitonasal
length shorter owing to shorter rostrum.

"_Reithrodontomys dychei nebrascensis_," named by Allen (1895:122)
from Kennedy, Nebraska, was distinguished in the original description
from _dychei_ by "slightly larger size, relatively longer ears, and
more strongly fulvous coloration." Allen applied the name _nebrascensis_
to harvest mice from Montana south to central Colorado and western
Nebraska. Howell (1914:30-31) placed _nebrascensis_ in synonymy under
_dychei_ because he found specimens from Kennedy to be "indistinguishable
from specimens of typical _dychei_ in comparable pelage." We concur
with Howell. Topotypes of _nebrascensis_ that we have examined average
only slightly paler than topotypes of _dychei_ in the same pelage (some
specimens from each series can be matched almost exactly), and do not
differ significantly in any external or cranial measurements. The
"fulvous" upper parts of the series from Kennedy (all taken in late
April) that was available to Allen resulted from worn winter pelage. We
think that Allen was led astray also by his erroneous assumption that
geographic variation in color of _R. megalotis_ on the Great Plains
paralleled that found in _Peromyscus maniculatus_. Actually, _R.
megalotis_ varies in color much less geographically in the region
concerned than does _P. maniculatus_.

Specimens from the northwestern part of the range of _dychei_ (Wyoming,
Montana and western South Dakota), like those from western Nebraska,
average slightly paler dorsally than topotypes and other specimens from
eastern Kansas and Nebraska (a few approach _aztecus_ in this regard),
but do not otherwise differ. Most specimens from northern Colorado,
southwestern Nebraska (Hitchcock and Dundy counties) and western Kansas
average slightly paler than typical specimens and have longer rostra,
approaching _aztecus_ in these particulars, but have the shorter ears
and shorter tail of _dychei_. In general, these intergrades resemble
_dychei_ to a greater degree than _aztecus_ and are accordingly assigned
to the former. One exception is a series from Muir Springs, 2 mi. N and
2-1/2 mi. W Ft. Morgan, Colorado. Specimens in this series approach
typical _dychei_ in color, but resemble _aztecus_ in having long ears
and long rostra (average 15.3 and 7.5