6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 73 



There are authentic records of other even greater tidal waves in 

 lower Florida. 



Without a doubt this process of enforced migration began as soon 

 as the Liguus spread over the island of Cuba, perhaps back in Miocene 

 or Pliocene times, but it is probable that no region existed to the 

 northward suitable for them to live in. Certainly if any colonies of 

 these snails existed in any part of what is now Florida before the 

 <jlacial epoch they were destroyed by its cold, for they are tropical 

 and can not stand hard freezing. 



A period of subsidence occurred for the State of Florida during 

 early or middle Pleistocene, and nearly all the eastern part of it and 

 all the lower end to just north of the Caloosahatchee River were car- 

 ried below sea level. A great bed of oolitic material, the Key West 

 limestone, was deposited over the area now occupied by the Lower 

 Keys. Another very similar set of beds was laid down along the 

 southeast part of what is now the mainland — the Miami limestone — 

 and a third on the southwest coast called the Lossmans River lime- 

 stone. A set of beds was formed in what is now the Everglades, at 

 first doubtless marine, then brackish, and finally fresh water. It is 

 probable that a coral reef, which afterwards became the Upper 

 Florida Keys began to develop during this subsidence, and it reached 

 from a short distance south of Cape Florida in a curved line to what 

 is now known as Newfound Harbor Keys, just south of Ramrod Key, 

 thus lapping over onto what is now the Lower Keys for a distance of 

 perhaps "5 miles. This was followed by an elevation during which 

 the land was probably raised to about the same height as at present. 

 The great bed of Key West limestone became a single island, reaching 

 from east of Johnson Keys to and including Key West and from the 

 Gulf of Mexico on the north to the Florida Strait on the south. The 

 sea began to form a low, broad shore elevation just within what is 

 now the southeast coast of the mainland from somewhere near Fort 

 Lauderdale to the south, then southwest, west, and again southwest 

 to near Whitewater Bay. This consisted of low ridges which formed 

 one after another as the sea retreated, leaving flats and shallow 

 lagoons between, and in these marine mollusks and other animals 

 lived and died undisturbed. Later this became a soft oolitic 

 limestone. . 



A great variety of seeds of tropical trees, shrubs, and plants was 

 carried by the Gulf Stream, a few possibly by migrating birds, and 

 some lighter ones by the wind and landed on the large southwest 

 island as soon as it was high and dry above the tide, and at once 

 a dense hammock growth was formed over much of the higher parts 

 of it. Seeds of the Caribbean pine {Pinus carihaea) were probably 

 blown across from Cuba and forests established on some of it and 



