Freshwater benthic shellfish.Pearls The shell is thick and has a slightly unequal triangle shape. The front part is short and low, the anterior dorsal margin is not obvious, the posterior long is high,Pearls and the posterior dorsal margin extends upward to form a large crown. The back of the shell has a series of gradually thickened longitudinal ribs from the top of the shell to the back. The trailing edge is round. The abdominal margin is nearly straight. The top of the shell is located about 1/6 of the length from the front shell, and there are several ribs on the top of the shell. Adult crowns often leave only scars,Pearls and larval shells are generally intact. The surface of the shell is dark yellowish green to dark brown,Pearls and the top of the shell is often eroded and loses the surface color. The hinge is strong and the ligaments are thick, Pearls located at the base of the crown. The left and right shells each have a tall rear tooth. The front teeth are weak,Pearls and there are several longitudinal protrusions and grooves below and behind the rear teeth. The anterior closed shell muscle scar is large in wedge shape,Pearls the extensor foot muscle scar is round,Pearls the anterior retractor foot muscle scar is small and deep, the posterior closed shell muscle scar is large and shallow,Pearls the coat muscle scar is wide, and the true pearl layer is shiny. Living on the muddy bottom of rivers and lakes and marshes,Pearls the action is slow.
Note: Most of the substances that make up pearls and shells are calcium carbonate. Calcium carbonate forms calcite and aragonite with different conditions during crystallization. Pearl is composed of aragonite and shell is a prism layer composed of calcite. Therefore,Pearls although they are both calcium carbonate crystals,Pearls due to the different crystal systems, they form different substances-pearls and shells.
