Thick-lipped pebblesnail
The thick-lipped pebblesnail, scientific name Somatogyrus crassilabris, was a species of freshwater snail with an operculum, an aquatic gastropod mollusc in the family Lithoglyphidae. This species was endemic to Baxter County, Arkansas in the United States. Its natural habitat was the north fork of the White River. It is now extinct. References

Somatogyrus
Extinct gastropods
Taxonomy articles created by Polbot
Endemic fauna of Arkansas
Species known from a single specimen
Baxter County, Arkansas