1910.] NATURAL SCIENCES OF PHILADELPHIA. 489 



Area sp. undet. 



A single right valve was taken representing another species having 

 more numerous ribs decidedly narrower than their intervals. As it 

 is somewhat imperfect, description is deferred. 

 Ostrea sp. 



Oysters occur in some quantity in a bed between Los Cahobas and 

 Formonde. The species has not been determined. Another oyster 

 bed was found in the mountains north of Lake Assuei. 



