The firefly species Photuris pensylvanica (DeGeer) has been the source of much taxonomic confusion. The species name P. pensylvanica (also P. pennsylvanica) has been applied erroneously for decades and as a result, entomological collections and publications are replete with misidentifications. In the absence of type specimens, Herbert S. Barber applied the name P. pensylvanica to the diminutive Mid-Atlantic tidal marsh-inhabiting “dot-dash” flashing species in 1951. To stabilize the genus Photuris Dejean, we made a concerted effort to locate the original type series, including the holotype, but were unsuccessful. As such, we briefly summarize the history of the taxon, accept Barber's designation, provide the first modern description of the species, designate a neotype from the proper type locality of Wilmington, Delaware, USA, and review its confirmed distribution. Thus far, the name-bearing taxon is recognized only from the freshwater tidal lowlands of the Chesapeake Bay and Delaware Bay estuaries. The species should be looked for in freshwater tidal marshes both north and south of these estuaries.