Cretaceous gastropods

Planorbis is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod molluscs in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.

Pleurotomaria is an extinct genus of sea snails, marine gastropod molluscs in the family Pleurotomariidae.