Editing Seashell (section)

=== Bivalves ===
{{main|Bivalvia}}
[[File:CoquillagesFadiouth.jpg|thumb|Single valves of the [[bivalve]] ''[[Senilia senilis]]'', plus two [[gastropod]]s, washed up on the beach at [[Fadiouth]], [[Senegal]]]]
Bivalves are often the most common seashells that wash up on large sandy beaches or in sheltered [[lagoon]]s. They can sometimes be extremely numerous. Very often the two [[valve (mollusc)|valves]] become separated.

There are more than 15,000 species of bivalves that live in both marine and freshwater.  Examples of bivalves are clams, scallops, mussels, and oysters. The majority of bivalves consist of two identical shells that are held together by a flexible hinge.  The animal's body is held protectively inside these two shells. Bivalves that do not have two shells either have one shell or they lack a shell altogether. The shells are made of calcium carbonate and are formed in layers by secretions from the mantle. Bivalves, also known as pelecypods, are mostly filter feeders; through their gills, they draw in water, in which is trapped tiny food particles.  Some bivalves have eyes and an open circulatory system.  Bivalves are used all over the world as food and as a source of pearls. The larvae of some freshwater mussels can be dangerous to fish and can bore through wood.

[[Shell Beach, Western Australia]], is a beach which is entirely made up of the shells of the [[cockle (bivalve)|cockle]] ''[[Fragum erugatum]]''.