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1581 



TERTIARY FAUNA OF FLORIDA J 



the correction * which is now generally accepted. A summary of the long and 

 somewhat complicated history of this formation is given by Hill f with de- 

 terminations of the foraminifera by Dr. R. M. Bagg, whose geological dis- 

 crimination has not kept pace with his undoubtedly wide knowledge of the 

 special group to which his studies are devoted, as he still refers the Vicksburg 

 to the Eocene, and does not discriminate it from the nummulitic series, while 

 he concludes that the Bowden foraminiferal fauna must be Miocene. This, 

 from the evidence of the molluscan and corallian fauna is undoubtedly a mis- 

 taken conclusion, the explanation of which, perhaps, lies in the suggestion that 

 the species of foraminifera which he limits to the Miocene began their career 

 earlier in the tropics, and reached more northern waters, where the foram- 

 iniferal fauna has been more thoroughly studied, a degree later in geological 

 time. Certainly the tropical forms like Nummulites, found in the Bowden 

 marl, are unknown in the typical Chesapeake Miocene of Maryland and Vir- 

 ginia. 



In the early descriptions of the molluscan fossils of Bowden many species 

 were referred to as identical with recent forms, a natural error, since there are 

 many which are the precursors of living forms and have their general aspect, 

 but which prove on critical study to be specifically distinct. The total number 

 of mollusks collected at Bowden by Henderson and Simpson, together with a 

 few described by Guppy which they did not obtain, amounts to four hundred 

 and thirty-five species, of which twelve per cent, appear to be identical with 

 recent species, while in the Chipola fauna, in which, on the continent, we find 

 the nearest analogue of the Bowden horizon, about 10.5 per cent, are recog- 

 nized as recent. The Miocene fauna of Duplin, the only one at present which 

 can well be compared with an Antillean fauna, has a little over eighteen per 

 cent, of its species identical with recent forms. The climatic changes which 

 modified the Oak Grove fauna and ushered in the temporary invasion of north- 

 ern species, which constitute the Alum Bluff Miocene fauna, affected both 

 those faunas in a way which makes them unsuitable for a direct comparison 

 with a continuously evolved marine population which, like that of the Antilles 

 since the Cretaceous, has been wholly sheltered from violent climatic changes. 



The most intimate relations of the Bowden fauna are with the somewhat 

 older Oligocene of Haiti and St. Domingo, which is still in great need of strati- 

 graphic elucidation. Gabb and others regarded all the Antillean Oligocene 



* Proceedings U. S. Nat. Museum, xix., No. mo, pp. 3O3~5 

 t Bull. Mus. Comp. Zoology, xxxiv., pp. 145-152, 1899- 



