Bivalves are soft-bodied invertebrates protected within two valves or halves of a shell. In the Pacific Northwest these animals include scallops, clams, mussels, and oysters.
The general anatomy of a bivalve is unusual as this animal is lacking some basic parts that other molluscs have such as a head! The shell of a bivalve is made of calcium carbonate, and the mantle secretes new shell material at the free edge enabling increased growth over time. A foot can extend beyond the bivalve’s shell and in some species this foot can move the animal away from predators, or help to bury the bivalve under the soft ocean floor.
Some bivalves have very long lifespans, like the Pacific geoduck which has been recorded living up to 168 years.