247] W. P. Woodring 49 



megodon Hanley is accepted, this species furnishes an example 

 of a former distribution on both sides of the Isthmus of 

 Panama and a present restriction to the Pacific side. Another 

 oyster probably is identical with the Eecent mangrove- 

 oyster, 0. folium Linnaeus. Although the species may not be 

 genetically valid, it may be assumed that the Bowden form 

 had the peculiar habits of the oyster that is frequently found 

 in mangrove swamps in the Antillean region. 



The family Limidae includes, in addition to the common 

 Lima, the rare Limcea. Likewise among the Anomindae is 

 found the uncommon Placunanomia, as well as the ubiquitous 

 Anomia. The brackish-water Dreissena is not frequently 

 encountered among American Tertiary faunas. Of greater 

 interest is the presence of the extremely rare Julia, a genus 

 that at the present time is confined to the Indo-Pacific region 

 and is represented by only a few fossil species one from the 

 Oligocene of Florida and two from the Miocene of south- 

 western France. 



A minor element in the fauna is furnished by the Anomalo- 

 desmacea. The five species are confined to the superfamily 

 Poromyacea and include small forms under the families Ver- 

 ticordiidae, Poromyacidae and Cuspidariidae. One of the 

 Cuspidarias is the type of the subgenus Bowdenia Ball. 



.The relative importance of the Teleodesmacea is dimin- 

 ished by the unusually large number of prionodonts, although 

 naturally the teleodonts include the bulk of the fauna. 

 Among the Astartacea members of the family Astartidae are 

 conspicuously absent, but the Crassatellitidae are represented 

 by five species of Crassatellites, of which the most important 

 and the most abundant belong to the subgenus Crassinella. 

 ISTo Carditas are present, but the genus Venericardia includes 

 a prolific Venericardia s. s. and also a small curious form 

 that has been referred to the subgenus Pteromeris, although 

 it is hardly typical of that group. 



The superfamily Lucinacea is the most diversified of the 

 larger groups. Although only five genera are included, they 

 are represented by 32 species. The genus Phacoides alone 



