Four species of mylagaulid rodents are described from the Tesuque Formation, Espanola Basin of New Mexico: Alphagaulus vetus (Matthew, 1924), Ceratogaulus robustus, new species, Notogaulus minor, new genus and species, and Notogauhis major, new species. Ceratogaulus robustus is distinguished from other species of the genus by its much heavier dentary and relatively wider premolar. Notogaulus is separable from other mylagaulines in its unique features of its cranium (ovate rugose areas on the nasals; shape, thickness, and porosity of bone on the postorbital processes), and relatively primitive dental morphology (no preferred separation of the branches of the parafossette on P4). The recognition of a distinct genus of mylagaulid from New Mexico demonstrates that by the middle Miocene (Barstovian) derived mylagaulines had evolved regionally into distinct genera.