The Pacific slope of North America's Cretaceous to late Eocene record of the pteriid bivalve Pteria Scopoli, 1777 is studied in detail for the first time. It is mostly represented by Pteria pellucida (Gabb, 1864) and Pteria clarki (Weaver & Palmer, 1922), which are redescribed and refined in their stratigraphic distributions. Pteria pellucida, known from southwestern Oregon and California, was previously reported ambiguously as being both Cretaceous and Eocene age but is actually restricted to the Late Cretaceous (early Turonian to late Santonian). Pteria clarki ranges in age from middle to middle late Eocene. It was previously reported as occurring only in Washington State but also occurs in California. Other species are Pteria lochi, sp. nov., of late late Campanian to possibly early Maastrichtian in age, and Pteria sp., of late Paleocene age; both are found in California. The definition of Pteria is expanded based on the presence of weak radial ribs on P. load sp. nov. The so-called Pteria bowel Nelson, 1925, from southern California and of late Paleocene age, has a hinge similar to that found in bakevelliids. Phelopteria Stephenson, 1952 is recognized for the first time as a junior synonym of Pteria. Specimens of the studied species were collected from shallow-marine, fine-grained siliciclastics that accumulated under warm-temperate conditions during the Late Cretaceous and under subtropical conditions during the Paleogene. Specimens are rare, except at a few localities. Pteria most likely originated during the Jurassic in the Old World Tethys Sea region. It arrived in the study area during the early Turonian, which coincided with the highest sea-level stand and the warmest waters of the Late Cretaceous.
