A recent review lists all forms ofEuneomysas a single species. We show in this report that two species live sympatrically at two localities in Chile and two in Argentina. The grooves on the anterior surfaces of the upper incisors are centrally positioned in one of the species and laterally positioned in the other. The species with central grooves has a larger head and body, larger hind foot, wider interorbital constriction, wider rostrum, longer molar toothrow, larger claws on the front feet, and lives in deep soils. The smaller species lives in bare, rocky habitat. The genusEuneomysthus comprises at least two species. The namesmordaxandchinchilloidesare appropriate for the large and the small species, respectively.