Dreissenidae

The Dreissenidae are a family of small freshwater aquatic bivalve molluscs, commonly called mussels although not at all closely related to true mussels. The shells of these bivalves are shaped somewhat like those of true mussels, which they also resemble in attaching themselves to a hard substrate such as stone using a byssus; however, this group is more closely related to the venus clams (Veneridae).