This is a study of silicified gastropods from carbonate strata of the Phosphoria rock complex of Lower to Middle Permian (Leonardian-Wordian) age in Wyoming. Twenty-five collections from 13 locations in western and central Wyoming were studied. Collections are from the Grandeur, Franson and Ervay Members of the Park City Formation, the lower member of the Shedhorn Sandstone and limestone tongues of the Phosphoria Formation. Gastropods are a minor but relatively diverse component of the faunas sampled. One new genus, Shedhornia, is recognized. Seven of the 55 species are described as new: Euphemites fremontensis, Bellerophon (Pharkidonotus) altitropis, Apachella boydi, Lamellospira alveozona, ?Gyronema clausepeakensis, Platyceras (Platyceras) yochelsoni, and Shedhornia ornata. Many taxa are indeterminate at particular taxonomic levels due to poor preservation. Several unexpected resemblances to Pennsylvanian faunas are noted.