USFWS determined threatened species status under the ESA 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. They 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 if finalized this rule under the authority of section 4(d) of the Act, 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. This rule is effective 27 July 2023. POC is John Weber, Field Supervisor, USFWS, Missouri Ecological Services Field Office, 101 Park DeVille Drive, Suite A, Columbia, MO 65203–0057; tele: 573–234–2132. (Federal Register 27 June 2023 [Rule] Pagefs 41724-41771)