Marine Pleistocene deposits have been traced along the Coastal Plain of the Gulf of Mexico from western Florida to Texas. The fauna is essentially similar to that inhabiting the Gulf of Mexico today. Marine fossils are found up to a few feet above sea level in western Florida and Alabama. However, in the vicinity of the Mississippi Delta the Pleistocene deposits have apparently been considerably tilted, probably because of the weight of the sediments brought down the Mississippi River. Marine Pleistocene fossils are found throughout this section to a depth of at least 2400 feet from the surface in the delta south of New Orleans. The depression caused by the Mississippi River is apparently limited in extent, and marine fossils are again encountered above sea level in the Pleistocene deposits near Lake Charles, Louisiana. It is suggested that at least some of the marine deposits of this region may be correlated with the Pamlico terrace of the Atlantic Coastal Plain and consequently date from the last major interglacial stage. It is further suggested that these same marine deposits can be correlated with the Beaumont formation of Texas.