Venerida (formerly Veneroida) is an order of mostly saltwater but also some freshwater bivalvemolluscs. This order includes many familiar groups such as many clams that are valued for food and a number of freshwater bivalves.
Venerids are generally thick-valved, equal-valved and isomyarian (that is, their adductor muscles are of equal size). Three main hinge teeth are characteristic of the subclass Heterodonta, to which this order belongs. Many species are active rather than sessile. However, they tend to be filter feeders, feeding through paired siphons, with a characteristic folded gill structure adapted to that way of life.[citation needed]
