• Unio is commonly known as freshwater mussel.

• Body is soft, unsegmented, bilaterally symmetrical and flattened, measuring about 5-10cm in length and enclosed in a calcareous shell.

• Shell consists of two separate equal pieces or valves covering the right and left sides of the body.

• Two valves of the shells are joined together by hinge ligament along the dorsal side.

• Umbo is situated near the anterior end of the dorsal side.

• Mantle consists of two lobes corresponding to the two valves of the shell.

• Foot is large, muscular and wedge shaped used for burrowing.