2oS TRANSACTIONS OF THE WAGNER FREE 



which it flourished may appropriately be designated as the Chesapeake epoch. 

 The fauna introduced at this time has left lasting traces on the fauna of the 

 Gulf of Mexico even to the present moment, but never reached as far south 

 as the Florida Keys or the southern portion of the peninsula. The faunal 

 change was decidedly the most important mutation which is traceable in the 

 fossil invertebrate faunas of the Gulf and Floridian region during the whole of 

 Post-Eocene time. 



The Chipola epoch here, in general, was a period of very slow and gentle 

 elevation, followed at or near its close by a slight depression equally gentle. 



The Chesapeake epoch in the South was in the main a period of quies- 

 cent deposition, and was closed by a very important movement in elevation. 

 In the Central American region (notably Costa Rica), the Miocene rocks were 

 elevated to a height of 12,000 feet above the sea. The Panamic connections 

 between the Caribbean Sea and the Pacific Ocean were definitely terminated, 

 and the connection between the continents of North and South America finally 

 brought about. On the northern shores of the Gulf of Mexico the elevation 

 was more moderate, but considerable, and by it the island of Florida was 

 united to the Georgian mainland and the previously existing strait perma- 

 nently closed. This event, in the classification proposed by the writer, termi- 

 nates the Miocene. 



The products of erosion resulting from the rising of the land 

 were probably those laid down as the Grand Gulf beds of Hilgard and 

 the Altamaha Grits of Georgia. The water in which they were deposited was 

 for the most part fresh or brackish, and the littoral subsidence so gradual as to 

 practically exclude the sea and its fauna. 



The Pliocene of Eastern America, as understood by the writer, begins 

 with the culmination of the movement in elevation just described, and ends 

 with the beginning of the Glacial period. 



The elevation on the continent resulted in the immediate increase of 

 fluvial erosion, and the continued and accelerated creation of perezonal forma- 

 tions similar to the above-mentioned Grand Gulf-beds, especially the Lafayette 

 or Appomattox formation of McGee. The discharge of immense quantities 

 of sediment must have rendered the shores less adapted to profuse molluscan 

 life than they had been during the Chesapeake epoch. At all events, the 

 Chesapeake fauna seems to have receded, and to have been gradually followed 

 up by the warm-water fauna which succeeded the Chesapeake and is pre- 

 served in the Caloosahatchie beds. As the peninsula of Florida has preserved 

 an unbroken record of this era, it would seem appropriate to apply to it the 

 name of the Floridian epoch, and, slightly modifying Prof Heilprin's use 

 of the term, to refer all deposits of similar paleontologic contents to a single 

 assemblage in the system under the name of the Floridian group. 



It is probable that the South American vertebrates, such as Glyptodoii, 

 which found their way northward after the union of the continents, did not 



