190 AMERICAN JOURNAL 



Closely resembles P. irradians, Lam., but has much less 

 prominent ribs, and is not ventricose. 



YENERICARDIA, Lam. 



V. MooREANA, Conrad. 



Description. — Cordate, thick, ventricose ; ribs 27 or 28, flat- 

 tened on the back, prominent, square, broader on the back than 

 beneath, or the interstices are narrowed at the surface by a 

 slight lateral carination of the ribs ; ribs prominent to the ven- 

 tral margin ; narrow, close and prominent on the anterior and 

 posterior slopes ; crenulated on the beak and umbo. Length 

 1| inch. 



Locality. — Texas. Dr. Francis Moore. Eocene. 



Distinguished from planicosta and densata by its size, by the 

 prominence of the ribs on the margin of the valves, and on the 

 anterior and posterior slopes, and by the interior marginal teeth 

 which are not carinated on the margins. 



