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JOURNAL OF CONCHOLOGY. 



YoL. I. FEBRUARY ib, 1865. No. 1. 



CATALOGUE OE THE EOCENE AND OLIGOCENE 

 TESTACEA OP THE UNITED STATES. 



BY T. A. CONRAD. 



The fossil shells in the following catalogue characterise two 

 consecutive Tertiary formations, the oldest of which has long 

 been regarded as an equivalent of the European Eocene. The 

 later formation I believe to be of the same age as the Oligo- 

 cene which immediately succeeds the Eocene. The fossils 

 of the latter formation indicate two very distinct periods or 

 stages which hold in common only two species so far as our 

 present collections indicate. The older Eocene species may 

 be known by the localities cited ; Maryland, Virginia and 

 New Jersey. Those of Claiborne, Alabama, are all upper 

 Eocene exclusively, except Venericardia planicosta, V. densata, 

 Cyclas Glaihornensis and Tarritella Mortoni. The Texan 

 species are probably upper Eocene. A few other species are 

 indicated in the catalogue as occurring only in the older divi- 

 sion of that formation. 



No species has been determined to be common to the Eocene 

 and Oligocene. The latter is indicated by the locality of 

 Vicksburg. 



