84 Bui^ivETiN 31 84 



hence interspaces becoming V-shaped ; tip of V somewhat trun- 

 cated, largely so in Midway forms called wilcoxensis by Dall ; 

 slopes of V showing irregularly directed growth-lines which more 

 or less criss-cross at the bottom of the V, also showing most 

 beautifully under a strong lens a fine granulation with a tendency 

 toward a radiate arrangement (pi. 30, fig. 12); from about ribs 

 24 to 25, or those from the umbonal ridge to about the fourth be- 

 low the ligamental margin the strength of the ribbing decreases ; 

 from about the fourth below the ligamental margin to the margin 

 itself the ribs become strong again, oftentimes the fourth being 

 the strongest and where it terminates on the posterior margin a 

 slight angle appears ; these sub-ligamental ribs are also more 

 strongly and irregularly ornamented than those below. 



7>/^.— Phila. Acad. Nat. Sci. 



Horizon. — Claiborne and St. Maurice of S. C. 



Specimens figured. — Paleont. Mus. , Cornell Univ. 



Localities. — Claiborne sand bed, Claiborne, Ala. 3 and 6 

 miles W. N. W. of Orangeburg, S. C. 



Venericardia complexicosia Aldrich and Meyer, PI- 31. Fig. 5. 



V. complexicosta Aid. and Mr., Jr. Cinn. Soc. Nat. Hist., vol. 9, pt. 

 II, p. 45, pi. 2, fig. 21, a. 



Original characterization. — Rather small. Cordate. Very much in- 

 flated. Beak large. Covered by compound, elevated ribs, crenulated near the 

 umbo. They consist of a large median and two small side-ribs. Margin 

 crenulated within, in correspondence with the outer ribs. 



Wautubbee. 



Venericardia mooreana Gabb, from Texas, and Ven. perantiqua Con. 

 ( V. subquadrata Gabb), from New Jersey have similar ribs, but are less in- 

 flated ; have a rounded ventral margin and a smaller beak. 



In our collections from Waubtubbee we have found nothing 

 corresponding to this description. But it is clear that we have 

 in this species a direct descendant of the small Woods Bluff Ven- 

 ericardias heretofore commonly referred to a variety of alticostala. 



Remarks on the rotunda-alticostata stock 



In specimens from Woods Bluff (pi. 31, figs. 1-4), note the 

 general terracing of the ribs as in natchitoches and alticostala ; the 

 tendency toward an angular outline as in trapaguara, carsonensis 



