Molluscs of the Natural Well Locality, Duplin Stratotype, Near Magnolia, North Carolina, and Rediscovery of Carinorbis Quadricostata (Emmons, 1858) (Gastopoda: Amathinidae)

Abstract

The Duplin Formation stratotype at the Natural Well limestone sink near Magnolia, North Carolina, is commonly thought to be the source of one of the most thoroughly documented Pliocene molluscan faunas in the Carolinas. However, few of the 196 species listed by Dall (1903) as from "the Duplin well or the adjacent village of Magnolia" were actually collected from Natural Well. Neither the coding of Dall's lists nor reference in text clearly indicates which specimens were collected from the stratotype section. A stratigraphically pure Natural Well collection, housed in the Geology Department of the University of North Carolina at Chapel Hill, contains 239 molluscan species (Appendix I). The faunule is low in endemics and high in first appearances of species that continue into the younger Waccamaw faunas . Like the correlative Tearcoat Branch and Muldrow Place faunules the Natural Well faunule contains only a single pectinid species, the ubiquitous Carolinapecten eboreus. The UNC-CH collections contain a number of rare and u nusual species, including a single specimen of Carinorbis quadricostata (Emmons, 1858). This is only the third recorded specimen of this rare and endemic species, and the first that permits comparative systematic analysis. The genus Carinorbis has been overlooked or inaccurately synonymized in most literature.