Evaluation of comparative material, including type specimens, of 2 derogenid species (Digenea: Derogenidae) in freshwater fishes of the families Cichlidae and Pimelodidae in Mexico revealed the invalidity of Genarchella luistoddi (Jiménez, Guajardo, and Briseño, 1981), a parasite of cichlid fishes in northern Mexico. This taxon is considered to be conspecific with Genarchella isabellae (Lamothe-Argumedo, 1977), originally described from the pimelodid Rhamdia guatemalensis (Günther) and frequently occurring in cichlids of the genus Cichlasoma in southeastern Mexico.