,4 Contribution to the Geologic History of the Floridian Plateau. 163 



Junction, and extends eastward until overlain b\' Pleistocene deposits. 

 There are certain peculiarities of this formation that should be noticed. 

 The following five species, collected at Nashua, Eupleura miocenica var. 

 intermedia Dall, Ilyanassa porcina Say, /. isogramma Dall, I. granifera 

 Conrad, and Nassa scalaspira Dall, occur in the Waccamaw Pliocene 

 of the Carolinas, but not in the Caloosahatchee marl of Florida. The 

 presence of Recten madisonius suggests Miocene in the same bluff, and 

 that both Miocene and Pliocene are represented, but the beds have not 

 been differentiated. 



Exposures of Pliocene marl occur at the following additional locali- 

 ties southward along the St. John's River: 0.5 mile above the Atlantic 

 Coast Line bridge over St. John's River, Putnam County; 0.5 mile south 

 of De Leon Springs Station, Volusia County, 5 miles below Sanford 

 railroad bridge, east side of St. John's River, and perhaps 7 miles below 

 Sanford railroad bridge. 



Proceeding southward the species belonging to the Waccamaw 

 fauna disappear; they are found only at Nashua; and the southern 

 exposures seem geologically \^ounger. In the exposure 7 miles below the 

 Sanford railroad bridge, every species might be Pleistocene, and the 

 exposure was tentatively referred to the Pleistocene because of its simi- 

 larity to the one 5 miles below the bridge. 



In the northern drainage ditch 6.5 miles west of Fort Lauderdale, 

 Mr. Matson obtained 17 species of fossils that were specifically identified; 

 16 of these are also Recent, and one, Stronibus leidyi, was not previously 

 known from beds younger than the Caloosahatchee. This exposure 

 was tentatively referred to the Pleistocene because of its relation to other 

 exposures definitely Pleistocene. These facts lead to the inference that 

 southward from Nashua younger Pliocene beds are encountered, and that 

 the Pliocene fauna is very gradually supplanted by that of the Pleistocene.* 



A considerable collection of Pliocene fossils was obtained from a 

 well on the property of Mary Boss, on an island in Lake TohopekaHga, 

 about 3 miles from Kissimmee, at a depth of 150 feet. The Pliocene is 

 here overlain by at least 100 feet of Pleistocene beds. 



The eastern Pliocene area overlaps the Miocene, and flanks the east- 

 ern side of the Apalachicola Group, extending southward along St. John's 

 River valley from Nashua to Sanford ; it is overlain on the east and south 

 by Pleistocene deposits, but is shown by well-borings to be present at a 

 depth of 150 feet in Lake Tohopekaliga. No surface exposures of marine 

 Pliocene are known between Sanford and Zolfo Springs on Peace Creek. 



The Caloosahatchee marl constitutes the second, the more southerly, 

 of the marine PHocene formations. The type locaHty is along the Caloosa- 

 hatchee River from Fort Thompson, near Labelle, to Olga. This river 

 stretch has been studied and described by Heilprin,^ Dall,^ Matson and 



* A collection made by me on North Creek, near Osprey, Manatee County, 

 furnishes additional evidence in favor of this opinion. Besides usual Pleistocene 

 species I also obtained at this locality specimens of Pyrazisinus scalatiis Heilprin, 

 a species previously known only from Pliocene beds. 



^ Wagner Free Inst. Sci., Trans., vol. i, pp. 22-33, 1887. 



^ U. S. Geol. Surv., Bull. 84, pp. 142-146, 1892, and Wagner Free Inst. Sci., 

 vol. Ill, pt. VI, pp. 1603-1614, 1903. 



