Unionidae

plural noun

Uni·​on·​i·​dae

: a very large family of freshwater mussels (suborder Submytilacea) having a pearly often roughly sculptured shell with a thick epidermis and larvae that pass through a glochidium stage and being represented in nearly all parts of the world but chiefly in North America where the nacreous shells of many of them are used for button making

Word History

Etymology

New Latin, from Union-, Unio, type genus + -idae

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