Nearly 200 years ago, a naturalist named Rafinesque stood on the banks of the Ohio River and began to describe the freshwater mussels he found there. Since that time these animals have become the most imperiled animals in North America. Dozens of species have become extinct, and it is estimated that two-thirds of the remaining freshwater mussels face a similar fate. Yet, despite their importance, the mussels of Ohio remain a poorly documented and...