Freshwater mussels and snails are members of the phylum Mollusca, invertebrate animals with a soft body that is enclosed wholly or in part in a mantel and a shell. Squid, octopuses, oysters, scallops and other shellfish are ocean-dwelling mollusks. There are nearly 300 species of freshwater mussels in North America, with most of these species in the eastern and midwestern United States. This mussel diversity has caused some biologists to call the U.S. "the rain forest of freshwater mussels." In fact, there are more different kinds of freshwater mussels in this country than on the entire African continent!