The species of Eumys Leidy, 1856, are reviewed. Six species are recognized and emended diagnoses are presented for the genus and all species. The enigmatic species, Coloradoeumys galbreathi Martin, 1980, is considered a new junior synonym of Eumys elegans Leidy, 1856; Coloradoeumys Martin, 1980, therefore becomes a new subjective synonym of Eumys Leidy, 1856. Additional specimens of Eumys cricetodontoides White, 1954, and Eumys parvidens Wood, 1937, are recognized and described. A new species, Eumys euryodus, from the Whitneyan of Nebraska is described. Size and proportional measurements of the molars, along with features of the occlusal morphology, are the major factors used to distinguish the species of Eumys.