85 St. Maurice and CIvAiborne Pei^kcypoda 85 



and alticostata ; and finally, the general shortness of the shell as 

 in carsonensis and rotu7ida, with the ribs ornamented by the fun- 

 nel-shaped nodules so well shown in the fu7igi7ia variety of ro- 

 hinda. 



The in-curving of the pronounced beak and the lack of de- 

 velopment in the post ero-basal region give this form a slight 

 Verticordia-li^Q. aspect. On passing into the St. Maurice stage 

 this often becomes more quadrangular, less inflated, and above 

 all seems to lose nearly all the terrace structure of the ribs in the 

 multicostate specimens. 



Table shoiving rotunda-alticostata relationship 

 Jackson {pmcisa tetrica carsonensis) eutawcolens 



Claiborne {fungi7ia rotunda fu7iiculus') alticostata 



flabelhitn coloradonis alticostata natchitoches 



St. Maurice trapaquara pera7itiqua 



complexicosta 



I 

 "alticostata f var." 



Sabine greggiana 



M id way wilcoxensis 



Ill-defijied and unrecog7iizable species of Venericardia described by 



Conrad. 



Proc. Phila. Acad. Nat. Sci., 1847, P- 297. From Eocene 

 Rocks, St. Matthew's Parish, Orangeburg District, S. C. 

 Cardita carolinensis 

 Suborbicular ? profoundly ventricose, with about thirty very promi- 



