Synoptic revision of the United States scarab beetles of the subfamily Dynastinae, No. 3: Tribe Oryctini (part)

This paper is the third in the series covering the United States dynastine scarab beetles and includes the four genera differentiated in the following key: 1. Apex clypeus acute and definitely bidentate, the teeth often worn and nearly obsolete. Apex clypeus acute, either sharply or bluntly so, but never bidentate. Mandibles definitely tridentate externally, the basal tooth often worn and barely visible; thorax not more than two-thirds the length of the elytra; color rufous to rufocastaneous or rufopiceous = Ligyrus Burmeister 2. Mandibles bidentate externally (caution: examine from below and laterally to avoid counting the lacinia teeth as third teeth of the mandible); thorax about three-fourths the length of the elytra; color always black. = Euetheola Bates 3. Thorax never foveate; mandibles large and evenly rounded externally, never toothed; coloration piceous to piceocastaneous, rarely rufocastaneous = Aphonides Rivers 4. Thorax always foveate at midapex, and with midapical tubercle; mandibles tridentate externally; coloration bright rufous and strongly shining = Oxygrylius Case