ABSTRACT
Southern and western subprovinces of the Carolinian Province Unlike the Caribbean and Brazilian Provinces, which are contiguous marine biogeographical entities, the Carolinian Province is divided into two separate sets of subprovinces. The bisected faunal pattern in the Gulf of Mexico is caused by the ecological barrier that is formed by the immense freshwater efuent of the wide Mississippi River Delta. This physical and ecological separation from the Suwannean Subprovince has resulted in the genetic isolation of the molluscan faunas of the western Texan and southern Yucatanean Subprovinces. Although they contain the full complement of Carolinian index taxa listed in Chapter 2 (and illustrated in Figures 2.2 and 2.3), the Texan and Yucatanean Subprovinces also have evolved their own distinct endemic faunas.
