Two once-common species of freshwater mussel now found in a handful of U.S. rivers are going on the Endangered Species List. The sheepnose and spectaclecase mussels will be protected under an agreement between the U.S. Fish and Wildlife Service and the Center for Biological Diversity. The spectaclecase has been eliminated from 20 of the 44 streams where it historically lived. The sheepnose has been eliminated from 25 of the 77 waterways where it historically lived. Past habitats included parts of the upper Ohio, Mississippi, Cumberland and Tennessee rivers. Freshwater mussels are considered key indicators of the health of waterways.