clam/muscle freshwater pearl mussel

I saw a mussel and it was in an oval shaped with a little circle on the right edge of it. It is brown on the edges but as the colors work their way into the center you can see it goes from brown to black with a smudge of brown. The mussel also has a hard shell protecting it. The mussel is mostly found in the southeast of the united states of America but mostly in Mississippi and Ohio. Mussels are mostly found in Freshwater. They eat Plankton. This is an Elongated Mussel and its name is the freshwater pearl mussel.