1 62 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



The Alachua Clays, with little doubt, represent the location of 

 such sinks, ponds or lakes. This view is supported by the local ex- 

 tent of the clay beds, the manner in which the fossils are imbedded, 

 as well as by the species that are found in the clay. Sinks very pos- 

 sibly began to form in central Florida as early as the late Miocene. 

 Sink formation must certainly have been active during the Pliocene, 

 and has continued in fact through the Pleistocene to the present. It 

 would seem, however, that the Pliocene was the time in which sink 

 hole ponds, small' lakes, and local surface streams reached their 

 abundant and typical development in this part of the State. An 

 analagous stage of development may be observed in adjacent sec- 

 tions of the State at the present time. 



The vertebrate fauna of the Dunnellon formation and the 

 Alachua Clays is practically the same, including the mastodon, rhi- 

 noceros, camel and early horse.* \\'ith these late Miocene or early 

 Pliocene forms is found Odocoileits, Tapirus, Megatherium and 

 other late Pliocene or Pleistocene types. The mixing of fossils re- 

 sults unavoidably from the manner of accumulation of the deposits, 

 for while the formation is believed to have accumulated chiefly dur- 

 ing the Pliocene, yet sink formation having continued later forms 

 were carried into the deposits and mixed with the earlier. 



The term "Alachua Clays," although descriptive of the local- 

 ities to which it was applied, yet is not applicable to the formation as 

 a whole. Since, however, this term has precedence in time, and is 

 also well established in literature, it seems advisable to drop the term 

 "Dunnellon formation," and to designate the deposits as a whole as 

 the Alachua formation. 



*The mastodon found in these deposits is M. floridanus. The horse is 

 Neohipparion, of which at least two species are present. The camel found in the 

 Alachua clay deposits, of which three species have been described, was identified 

 by Leidy and Lucas as Procanielus. Two species of rhinoceros are also recog- 

 nized, namely Teleoceras fossiger and Aphelops nialachoriniis. 



