i8 



BUI^LHTTN 39 



190 



Titrris albida Perry West Indian 



Glyphostoma dentifera Gabb West Indian 



Adeocina biillata Kiener var. costaricayia Olsson West Indian 



Adeocma reda d'Orb. West Indian 



Volvula cylijidrica Gabb West Indian 

 Andstrosyrinx elegans Dall variety West Indian 

 Marginella ave?ia Valen West Indian 

 Murex messorius Sowerby West Indian 

 Bursa a^assa Dillwyn West Indian 

 Natica canrena Linne West Indian 



Ardiitedo7iica graniilata \^2Lm.2iXQk. West Indian nnd Pacific 

 Astralium brevispinum Lamarck, variety basalts 



Olsson West Indian 



Astralium cadatum Gmelin West Indian 

 Sistrum 7iodidosum C. B. Adams West Indian 

 Lalirus iufundibuluvt Gmelin West Indian 

 Northia northicB variety iniocenica Olsson Pacific 

 Crepidula plana Say West Indian 

 Xenophora condiyliophora Born West Indian 

 Oliva testicea Lamarck var. costarice7isis 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- 



