Costa Rica Miocene — Olsson 



15 



Chione tegulum Brown and Pilsbr}^ 

 Pitaria cora Brown and Pilsbr}^ 

 Dosinia delicatissima Brown and Pilsbry 

 Petricola millestriata Brown and Pilsbry 

 Cy dine I la gatiuiensis Dall 

 Thracia gatiuiensis Toula 



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

 eral very distinctive species of which the following are most 

 important: 



Amusinm Lyonii Gabb 



Area dariensis Brown and Pilsbry also Lower Gatun 

 dementia dariena Conrad also Lower Gatun 

 Ca7icellaria {Aphera) islacolonis Maury 

 Neverita nereidis Maury 

 Sconsia cocleana Olsson 

 Scaphella costaricaiia Olsson 

 Ptychosalpinx f dentalis Olsson 

 Dentalium uscarianum Olsson 



The Gatun is the great fossil bearing formation of northern 

 Costa Rica and Panama, and is characterized by a rich and high- 

 ly diversified fauna. This fauna at the present numbers nearly 

 400 species, but additional collecting will doubtless add consid- 

 erably 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 type, 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 heav}^ thick-shelled species of 

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

 mon and characteristic: 



Area MaeDo7ialdi Dall Marginella MaeDonaldi Dall 



Area Pittieri Dall Valuta Alfaroi Dall 



Peeten levicostatus Toula Stronibus pugiloidis Guppy 



