The broad and imprecise type localities of Crotalinus catenatus Rafinesque, 1818 (now Sistrurus catenatus) and Crotalinus viridis Rafinesque, 1818 (now Crotalus viridis) are re-identified based on a published account of the collector's travels as well as an examination of the relationship and contacts between the collector and the author of the type description. Both type specimens are lost. Unfortunately, enhanced resolution of the type locality of S. catenatus places it within the range of S. c. tergeminus Say, 1823 (a subsequently described subspecies). Thus, the name S. c. catenatus incontrovertibly applies to the form currently recognized as S. c. tergeminus, which in turn renders the latter as a subjective junior synonym of the former, leaving the eastern form with an unfamiliar name (Crotalus messasaugus Kirtland, 1838). To conserve prevailing usage, we are preparing an appeal to the International Commission of Zoological Nomenclature (ICZN) to allow a neotype of Sistrurus catenatus to be designated from the type locality of Crotalus massassaugus. In the interim, existing use of the names should be continued. (c) 2008 by the American Society of Ichthyologists and Herpetologists.