The diagnostic potential of dorsal and anal pterygiophore-interdigitation patterns was examined in larvae of striped bass Morone saxatilis, white bass M. chrysops, white perch M. americana, and yellow bass M. mississippiensis. The number and position of pterygiophores relative to interneural spaces 1–6 and 10–13 and to interhaemal spaces 12–15, as well as total number of dorsal and anal pterygiophores, are characters useful in delimiting larvae of these species. Interdigitation patterns useful in distinguishing yellow bass from white perch larvae were not found; however, these two species may not co-occur.