Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for Western Fanshell and ‘‘Ouachita’’ Fanshell and Designation of Critical Habitat

We, the U.S. Fish and Wildlife Service (Service), determine threatened species status under the Endangered Species Act of 1973 (Act), as amended, for the western fanshell (Cyprogenia aberti), a freshwater mussel species from Arkansas, Kansas, Missouri, and Oklahoma, and the "Ouachita" fanshell (Cyprogenia cf. aberti), a freshwater mussel species from Arkansas and Louisiana. We also designate critical habitat for both species. In total, approximately 261.4 river miles (420.7 kilometers) in Arkansas and Missouri fall within the boundaries of the critical habitat designation for western fanshell. In total, approximately 227.7 river miles (366.5 kilometers) in Arkansas fall within the boundaries of the critical habitat designation for "Ouachita" fanshell. In addition, we finalize a rule under the authority of section 4(d) of the Act that provides measures that are necessary and advisable to provide for the conservation of these species. This rule extends the Act's protections to these species and their designated critical habitats.