iSy Costa Rica Miocene — Olsson 15 



Chione tegulum Brown and Pilsbry 

 Pitaria cora Brown and Pilsbry 

 Dosi7iia delicatissiina Brown and Pilsbry 

 Petricola millestriata Brown and I'ilsbry 

 Cyclhiella gaiunensis Dall 

 Thracia gatunensis Toula 



The Uscari fauna is still poorly known, but it includes sev- 

 eral very distinctive species of whicla the foUov/ing are most 

 important: 



Amusinm Lyonii Gabb 



Area dariensis Brown and Pilsbry also Lower Gatun 

 Cleme?itia dariena Conrad also Lower Gatun 

 Canccllaria {Aphera) islacolonis Maury 

 Neverita nereidis Maur}^ 

 Sconsia cocleana Olsson 

 Scapliella costaricana Olsson 

 Ptychosalpinx ? dentalis Olsson 

 Dentaliutn uscariayium Olsson 



The Gatun is the great fossil bearing formation of northern 

 Costa Rica and Panama, and is characterized b}^ a rich and high- 

 ly diversified fauna. This fauna at the present numbers nearly 

 400 species, but additional collecting will doubtless add consid- 

 erabl}^ to this number. As we have already noted the Gatun 

 beds present two important facies, the sandy and highly clastic 

 phase of the typical Gatun, and the deeper water t3^pe, illustrat- 

 ed by the coralline limestones and their associated marls. These 

 lithological types have their own more or less peculiar and dis- 

 tinctive faunas. 



The typical Gatun is the more common phase and is charac- 

 terized by a molluscan fauna of heavy, thick-shelled species of 

 littoral forms. In Costa Rica, the following are the most com- 

 mon and characteristic: 



Area MacDonaldi Dall Marginella MaeDonaldi Dall 



Area Pittieri Dall Valuta Alfaroi Dall 



Pecten levicostatus Toula Strombus pugiloidis Guppy 



