New omomyid primates (Haplorhini, Tarsiiformes) from middle Eocene rocks of west-central Hot Springs County, Wyoming.

Three new genera and four new species of omomyid primates constitute the first record of the Primates from upland middle Eocene rocks of Wyoming. One of these, Strigorhysis, gen. nov., possesses broadly basined molars with highly crenulated enamel which probably indicates a good deal of tough vegetable matter in its diet. Each of the new genera could have descended from known Wasatchian or early middle Eocene anaptomorphines: Aycrossia, gen. nov., is a plausible derivative of Tetonius or Chlororhysis; Strigorhysis, gen. nov., is most similar to Absarokius noctivagus; and Gazinius, gen. nov., most closely resembles Absarokius and Anaptomorphus. The anaptomorphines were probably equally as diverse as the better documented omomyines in the middle Eocene, but may have preferred upland environments at the margins of the Tertiary basins of the Rocky Mountain Interior.