Highnut
The highnut (Pleurobema altum) was a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. This species was endemic to rivers of the United States. Unionids are vulnerable to habitat change and are a highly endangered taxa (70% of them are considered imperiled). References

Pleurobema
Bivalves described in 1854
Taxa named by Timothy Abbott Conrad
Taxonomy articles created by Polbot