Ouachita pebblesnail
The Ouachita pebblesnail, scientific name †Somatogyrus amnicoloides, was a species of small freshwater snail with an operculum, an aquatic gastropod mollusc or micromollusc in the family Hydrobiidae.
The species was endemic to the United States. Its natural habitat was rivers, and it was named after the Ouachita River. The species is now extinct.