FREE INSTITUTE OF SCIENCE 



1545 



TERTIARY FAUNA OF FLORIDA 



By the researches of Professor R. T. Hill * and Mr. T. W. Vaughan much 

 more light has been thrown on the subject. 



I am entirely unable to accept Dr. Spencer's hypotheses ; while admitting 

 many of the facts he brings forward, I am convinced that they admit of some 

 other explanation. We find in the Oligocene of Bowden landshells belonging 

 to groups peculiar to and now inhabiting the island of Jamaica, which is suffi- 

 cient evidence that since the era during which the Bowden marl was deposited 

 the island has never been entirely submerged. With Cuba it may be different, 

 though I can hardly bring myself to believe that the peculiar landshell fauna 

 which is so characteristic of that island can have been evolved since the Pleisto- 

 cene. However, this question is apart from those we have to consider here. 



The proximity of Cuba to Florida and the fact that the adjacent portions 

 are composed of organic limestones, which has long been known, led to the 

 very natural but erroneous inference that Cuba and the peninsula were formerly 

 continuous, and that the Florida Strait had been cut between them by the ero- 

 sion due to weather and streams, and subsequently by the Gulf Stream. 



There is no doubt Cuba has been subjected to great geological convulsions, 

 but that any considerable part of the island has been submerged since the 

 beginning of the Miocene seems extremely doubtful and requires proof not 

 hitherto forthcoming. 



According to Mr. Vaughan's observations the great mass of the Tertiary 

 limestones of Cuba are middle and upper Oligocene, ranging from the Chatta- 

 hoochee to the Bowden or its equivalent. The Vicksburgian and the Miocene 

 are alike absent, no positive identification of Pliocene beds has been made, and 

 the Pleistocene reef rocks do not occur above the sea at a greater height than 

 thirty or forty feet. 



The, on the whole, remarkable horizontality of the Floridian strata indi- 

 cates a freedom from violent changes of level from the time the Peninsular 

 limestone first emerged from the sea. Landshells in the Ocala limestone show 

 that then dry land existed. South of the Suwannee Strait, closed in late Mio- 

 cene times, there is no evidence of subsequent submersion to any serious extent. 

 Two gentle flexures run parallel with the peninsula, having the lake district 

 between them ; a tilting of, at the most, thirty feet, up at the east, down at the 

 west, which may have been contemporaneous with the flexures : and, for the 

 rest, verv slow and slight but probably nearly continuous elevation never ex- 

 ceeding one hundred feet and perhaps less than half that, with dry land and 



* Bull. Mus. Comp. Zool., xvi., No. 15, pp. 243-288, 1895. 



