54 Bulletin 9 346 



by very minute concentric lines on the median portion, dying 

 away anteriorly and posteriorly ; anterior series of teeth slightly 

 curved; posterior series nearly rectilinear causing the margin of 

 the shell half way from beak to posterior extremity to be slightly 

 elevated ; pallial sinus deep ; a slightl}' depressed area extending 

 from the beak to the posterior basal and superior margin. 



The Midwaj^ specimens are varietally distincft from the Lig- 

 nitic. 



Localities. — Alabama : Woods Bluff. 



Type. — Woods Bluff ; Paleont. Museum, Cornell University. 



Venericardia planicosta, Pi's. 9, & 10. 



Syn. See Bull. Amer. Paleont., vol. i, p. 172; add: — 



Cardita dejisata Con., Jour. Acad. Nat. Sci. Phila., vol. i, p. 130, 



pi. 14, fig. 24, 1848. 

 Cardita planicosta Tuomey, ist Biennial Rep't Geol. Ala., pp. 146- 



147, 1850. 

 Cardita planicosta Tuomey, 2d Biennial Rep't Geol. Ala., p. 270, 



1858. 

 Venericardia planicosta Con. (Heilp. ), Proc. Acad. Nat. Sci., 



Phila., 1880, p. 366, foot-note. 

 Venericardia planicosta Aid., Bull, i, Geol. Surv. Ala., pp. 50, 53, 



55, 57, & 58, 1886. 

 Venericardia planicosta Smith & Johnson, Bull. 43, U. S. Geol. 

 Surv., pp. 40, 44, 45, 50, & 51, 1887. 



Lamarck's original description. — See Bull. Amer. Paleont., 

 vol. i, p. 172, 1896. 



It has already been shown how great are the variations of this 

 species in the oldest Eocene or Midway stage. In the Lignitic a 

 vast number of variations have been noticed, but to describe them 

 in detail would require a great number of plates and several hun- 

 dred pages of text. The subjecft will here be dismissed with sim- 

 ply the following remarks. 



Form oc. This is sub-circular in outline with the exception of 

 the beak, and is remarkable for its paucity of ribs. These are 

 about twenty-three in number, and near the umbo are narrower 

 than the interspaces ; in the center of the shell ribs and inter- 

 spaces are of about equal width ; near the base margins the ribs 

 increase rapidly in width and in some specimens coalesce. Local- 

 ities for this form are Nanafalia (occasionally) at the base of the 

 Lignitic, and four miles above Hamilton bluff on the Alabama 

 river, near the summit of the Lignitic. 



