Pelecypods (clams) are bivalved mollusks and are common in the oceans and streams of the world today. Pelecypod fossils are common in some places in Kentucky, but they are often confused with the more abundant brachiopods. Although both brachiopods and pelecypods have two valves (shells), they are quite different. Typically the two shells of a pelecypod are alike except that they are mirror images of each other. The two shells of the brachiopod are not alike. The animal living inside the brachiopod shell is very much different compared to the one living in the pelecypod shell. Brachiopods are rare today.