^93 



Costa Rica Miocene— Olsson 



21 



stratigraphic unit, and Gabb insisted that no division was possi- 

 ble. Dr. Maury however, as a result of paleontologic studies 

 from collections carefully made in the field, was able to divide 

 the Dominican Miocene into two formations, which she called 

 the Gurabo and the Cercado. To these Vaughan and his as- 

 sociates, in more recent stratigraphic work on the island, have 

 added 4 other subdivisions. The present recognized subdivisions 

 of the Dominican Miocene are: 



Mao clay 



Mao Adentro limestone 

 Gurabo formation 



{Sconsza laevigata zone) 



Cercado formation 



{^Aphera islacoloftis zone) 

 Baitoa formation and Bulla 

 conglomerate 



The relation of the Costa Rican and Panama Miocene to 

 that of Santo Domingo is extremely close; there being about 

 90 species in common. Of this number about 21 are recent, 

 about 26 species appear to be restricted to the Gurabo, some 27 

 species are common to both the Gurabo and Cercado formations, 

 and only it species are confined to the Cercado. The list of 

 of COvSta Rican and Panama species in the Dominican Miocene, 

 is as follows: 



Nucula tenuisculpta Gabb Cercado and Gurabo 



^Arca occidentalis Phil Cercado and Gurabo 



^Arca umbo7iata Lamarck Cercado 



Area Maury cB Olsson Gurabo 



Area Henekeni Maury Cercado 



Area golf oyaquen sis Maury Cercado and Gurabo 



Area chiriquie?isis Gabb Gurabo 



^Area aurieulata Lamarck Gurabo 



MIDDLE 



I,OWER 



*Recent 



