NO. 12 STRONG AND HERTLEIN : MARINE MOLLUSKS 181 



of Peru stated that about 17 per cent of the species recorded from the 

 Miocene of Peru occur in Caribbean deposits or have related forms in 

 those beds. He suggested that this relationship of the marine mollusks 

 of the Peruvian and Caribbean Miocene faunas is due to an oceanic 

 connection and that "until near the close of the Miocene, two or more 

 straits along geosynclinal troughs connected Pacific and Atlantic waters 

 and it is through these straits that faunal intermingling took place." 



One of the difficulties of determining the exact time and direction 

 of migration of marine mollusks between the two areas is the lack of 

 agreement of authors regarding the exact time units represented by the 

 Mid-Tertiary strata of the Caribbean region. An example of this is the 

 great divergence of views published by workers on the age of the 

 Bowden fauna of Jamaica. The beds containing this fauna were for 

 some time considered by many authors to be Oligocene in age. The 

 results of work within the past few years indicate rather definitely that 

 the fauna of the Bowden beds is at least as late as upper Middle Mio- 

 cene. Whatever the location and duration of these ancient interoceanic 

 connections in this region, there are a number of species in the present- 

 day molluscan fauna of western Panama that have been considered by 

 several workers to be identical with, and there are certainly quite a 

 considerably greater number of species which are analogous to, those 

 occurring living or fossil in the Caribbean region. 



The present collection obtained by shore and shallow water dredg- 

 ing contains 336 species of mollusks. The assemblage consists of the 

 following: 1 brachiopod, 91 pelecypods, 2 scaphopods, 242 gastropods. 

 Five of the species of gastropods are not positively identified but have 

 been compared to known species and in 10 additional ones the genus 

 only is definitely known due to poor preservation. Forty-six species are 

 described as new. All of the new species are small gastropods, and a 

 special effort was made to secure these small forms, due to the fact that 

 heretofore these have been largely neglected for the larger and more 

 brightly colored forms found in the region. In the present collection 

 it is noticed that a rather large number of species represent certain 

 genera, such as Area (11), Tellina (7), Anachis (10), Odostomia 

 (13), Turbonilla (21). 



Collections were made during the latter part of December, late In 

 January, and early in February. The collecting stations were as follows : 



Loc. 27,228 (C.A.S.). Just off Taboga Island, Gulf of Panama, 

 between Taboga Island and Uraba Island, in the channel, in 3 to 9 

 fms. L. G. Hertlein collector, Feb. 1, 1932. 



