_Remarks._--From _Reithrodontomys megalotis aztecus_, geographically adjacent to the southwest, _R. m. dychei_ differs as follows: upper parts averaging darker (especially 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_.