Bulletin 39 190 



Turris albida Perry West Indian 

 Glyphostoina dentifera Gabb West Indian 

 Adeochia bullata Kiener var. costaricana Olsson West Indian 

 Acteocina recta d'Orb. West Indian 

 Volvula cylindrica Gabb West Indian 

 Ancistrosyriyix elegans Dall variety West Indian 

 Marginella aveyia Valen West Indian 

 Murex messorhcs Sowerby West Indian 

 Bursa crassa Dillwyn West Indian 

 Natica carirena Linne West Indian 



Architedonica grantilata Lamarck West Indian nnd Pacific 

 Astralium brevispinum Lamarck, variety basalts 



Olsson West Indian 

 Astralium caelaturn Gmelin West Indian 

 Sistruvi 7iodulosujn C. B. Adams West Indian 

 Latirus iufundibnluvi Gmelin West Indian 

 JVorthia northicB variety miocenica Olsson Pacific 

 Crepidula plana Say West Indian 

 Xenophora conchyliophora Born West Indian 

 Oliva testicea Lamarck var. costaricensis Olsson 



It is but natural to expect that the Miocene beds along the 

 northern or Caribbean coast of Central America, should contain 

 a fauna largely ancestral to that of the present Caribbean, but 

 along with these strictly Caribbean t3^pes, we also find several 

 species, identical or closely related to forms now resticted to the 

 Pacific side. Their occurrence in Caribbean deposits points to a 

 connection between the Atlantic and Pacific oceans during Mio- 

 cend time and allows for a certain intermingling of their faunas. 

 Geological observations indicate that there were at least two 

 such straits crossing Central America during the Miocene, the 

 main one across Costa Rica, and a second through the Darien of 

 eastern Panama. 



This Pacific element of the Gatun fauna comprises many of 

 the most common and characteristic species. Certain of these 

 species had a wide distribution in the West Indies during Mio- 



