These belong to a group called Bivalvia, which means 'two vales'. They are molluscs and the soft-bodied animals lives inside the shell valves. When the animal inside dies, the ligament which holds the valves together, breaks and the shells are often found washed up on the beach.

Bivalves are filter feeders and their main source of nutrition is plankton. They live almost everywhere – on the rocky shores and also in freshwater habitats.