20 Bulletin 39 



and Pleistocene beds of Central America contain a well-marked 

 Pacific element in such species as Northia northics Gray Oliva 

 testacea Lamarck and Peden ventricosus Sowerb5^ 



Correlation 



Miocene rocks are now known from a great many localities 

 in the West Indies and the general Caribbean area of Central and 

 South America. In these areas they comprise a very important 

 series of sedimentary formations. Beds equivalent to the Gatun, 

 appear to be the most widespread and generally are highly fossil- 

 iferous. 



The following chart showing the equivalence of the Miocene 

 horizons in the West Indies and elsev/here to those of Central 

 America, does not differ materially from the more recent correl- 

 ations proposed by Maur}^, Cooke or Vaughan, except in the ad- 

 dition of the Uscari to the Lower Miocene of Panama and Costa 

 Rica. The Gatun formation is here recognized as being of Mid- 

 dle Miocene age with possibly some of its upper beds having 

 L^^pper Miocene affinities. The Gatun, at its type locality in the 

 Central Zone, is not more than 500 to 600 feet thick. In Costa 

 Rica it is ver^^ much thicker, and its higher beds ma)^ range into 

 the Upper Miocene. It is the exact equivalent of the Chesapeake 

 Miocene of the eastern United States. In this correlation, I have 

 been guided -not only b}^ the paleontologic evidence, but also by 

 the field relations of the formations, studied over a wide rage of 

 countr}^ in Costa Rica, and in Panama as far east as the Colombia 

 frontier. 



Santo Domingo Miocene 



In Santo Domingo and in Llaiti, Miocene rocks are exposed 

 in several areas, but attain their best development along the val- 

 ley of the Rio Yaque del Norte in the northern part of the is- 

 land. These beds are highl)^ fossiliferous and because of the fine 

 perservation of their fossils, have repeatedh^ attracted the atten- 

 tion of paleontologists. 



The earlier writers dealing with the paleontology of the Do- 

 minican Miocene, believed that it represented but a single 



