Pteriomorphia

The Pteriomorphia are a subclass of saltwater clams, marinebivalvemolluscs. They contain several major orders, including the Arcida, Ostreida, Pectinida, Limida, Mytilida, and Pteriida. It also contains some extinct and probably basalfamilies, such as the , , Bakevelliidae, Cassianellidae, and Plicatostylidae.

This subclass of molluscs has lamellibranchgills, and is epibenthic. Some attach to the substrate using a byssus. The foot is reduced. The mantle margins are not fused. Gills are usually large and assist in feeding. This group includes the well known mussels, scallops, pen shells, and oysters. It also includes the only members of the class bivalvia to have rudimentary eyes.