PELECYPODA—TELEODESMACEA. 545 



Ribs flat on central part of shell, tuberculated on anterior and 

 posterior portions. 



Midway : Gulf region. 

 512. V. alticosta Conrad. (Fig. 745.) Eocenic. 



k\G. 745. Venericardia alticosta, right valve. (After Harris.) 

 Fig. 746. Venericardia planicosta vzx. regia, X /^- 



Ribs about 22, much elevated and nodulose ; those on anterior 

 side are laterally keeled. 



Claibornian and Jacksonian of Alabama and Louisiana. 



513. V. planicosta Lamarck. (Figs. 746 and 747, a.) 



Eocenic. 

 Large, with length at times of 3 or 4 inches. 

 It has been proposed by some authors to distinguish the Ameri- 



Fig. 747. Venericardia planicosta, left valve, and V. smithi, right valve. 

 (After Harris.) 



can representative of the V. planicosta of Europe by the varietal 

 name of regia. 



