Arc form pearly mussel

The arc-form pearly mussel or sugarspoon, scientific name Epioblasma arcaeformis, was a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. No live individuals have been observed since the early 20th century and it is presumed to be extinct.

This species was endemic to the drainages of the Cumberland River and the Tennessee River in the United States. Its natural habitat was rivers. Like most other members of its genus, it became extinct due to habitat loss from pollution, impoundment construction, and canalization.