Recent biodiversity studies, reported here for the first time, have shown that the molluscan fauna of the Gulf of Mexico is far richer and more complex than previously thought. As a result of these new discoveries, the Gulf malacofauna is shown to contain large numbers of endemic species that reside within four separate biogeographical subdivisions of the larger Carolinian Molluscan Province: the Floridian, Suwannean, Texan, and Yucatanean Subprovinces...