Gaufinia is proposed as a new genus for the Sweltsa lamba (Needham and Claassen 1925) species group, and 5 current and 6 new species are recognized based primarily on scanning electron microscopy of the male epiproct. Males of the new genus are distinguished from all other Chloroperlidae by the presence of a distinctive leaf-like aedeagal lamella. A preliminary key for males of the 11 currently recognized species is presented to assist in identification.