|Pectinidae, the scallops, have shells that are ovate, fan-like (narrower at the beaks), with flat projections (called "wings" or "ears") either side of the beaks. Most have radiating ridges that may or may not be scaly. Some attach to soft substrate using byssal threads. Others just lay on the soft sediment. When disturbed, they can flap their valves and "swim" away from predators. This family, along with the true oysters (Ostreidae), have only 1 muscle (thus 1 muscle scar) compared to most bivalves that have 2 muscles. Many species are of important commercial value as food, as well as in shell collecting. There are 8 species found in Texas waters.