December, 1S44.] 173 



The Committee on Mr. Conrad's paper on new fossil 

 shells of the United States, reported in favor of publication. 



Descriptions of eight new Fossil Shells of the United States. 



By T. A. Conrad. 



Miocene Species. 



Crefidula. 



Crepidula cymbseformis. Elliptical, very profound or ventricose ; thick 

 about the region of the beak; apex inclined towards the left margin, acute, 

 separated from the margin of the aperture ; umbo compressed, prominent ; 

 aperture dilated above the middle and rapidly narrowed towards the end 

 opposite the beak ; diaphragm concave and remote from the margin. Length 

 1| inch. 



Locality. Petersburg, Virginia. 



The boat-shaped outline of this shell serves to distinguish it. from its con- 

 geners. It is the deepest or most ventricose of all the smooth species of the 

 Union. 



Eocene species. 

 Cardita. 



Cardita densata. Obliquely cordate, ventricose, thick, with about 

 twenty-five flattened costaj, obsolete towards the base, narrow, profound, 

 elevated and crenulated on the umbo ; umbo very prominent at the apex ; 

 anterior basal margin obliquely subtruncated ; posterior extremity truncated, 

 direct; cardinal area very thick and dilated, the teeth oblique. Height If 

 inch. Length the same. 



Locality. Claiborne, Alabama. 



This pretty species abounds in entire specimens in the argillaceous stratum 

 near low water mark in the Claiborne Bluff. I found none in the upper 

 beds. Compared with C. planicosta, it is much smaller, comparatively 

 shorter, thicker, and may always be readily distinguished by the crenulated 

 ribs on the umbo. 



Cytherea. 



Cytherea subimpressa. Ovate, slightly ventricose, smooth and polished, 

 with concentric slightly impressed lines on the anterior side ; anterior side 

 short, rather acutely rounded ; posterior side produced, acutely rounded at 

 the extremity ; dorsal margin long, oblique, slightly curved ; beaks promi- 

 nent ; lunule lanceolate, defined by a slightly impressed line. Length l£ inch. 

 Height JL inch. 



Locality. Marlbourne, Hanover county, Virginia. Mr. Ruffin. 



