This is mussels, molluscs, petabranchia. Pearl mussel family; Toothless mussel A general term for shellfish. Distributed in Asia, Europe, North America and North Africa. Most of them can naturally form pearls in the body. The shape is oval or oval. Thin shell. Fragile. The two shells spread out, sometimes with hind wings on the back. The top of the shell is broad and slightly convex, located in the middle or front of the trailing edge. The shell surface is smooth, with concentric growth lines or green radiation from the top of the shell to the abdominal edge. The gluing part is narrow and toothless. The shaft and feet are developed. Dioecious. Meat is edible, and it is also a natural bait and feed for fish and poultry. Some varieties can be used as freshwater pearls.

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