Bulletin 31 188 



so we are inclined to adopt the name com-Pressa for this particular 

 species. De Gregorio illustrates well the young stage of this 

 species (as perdubia) but he too indicates that its size is too 

 great. 



When specimens are young there is generally a flatness, a 

 broadness of posterior, a forward curving of the beak reminding 

 one (when viewed under the microscope) of Venus rileyi. The 

 valves are not distinctly dissimilar when young. The senile 

 stage, not often represented, shows a thickening, a geniculating 

 medially, an increase in regularity and strength of the growth' 

 lines, a sharpening of the posterior sub-margin and a channel on 

 the post-umbonal slope (shown best on decorticated specimens.) 



We strongly suspect that Dall had in hand some representa- 

 tives of this species along with others and classed them as C. ( Cu- 

 neocorhda) gregorioi (Trans. Wag. Ill, p. 843) in 1895. He re- 

 gards our sviithvillensis as synonymous with gregorioi. His vo.- 

 \^r'^XQ.\.2X\on oi perdubia (op. cit. p. 844) is not clear, owing to 

 lack of illustrations and to the fact that three-fourths of his 

 "Jackson Eocene" localities are really St. Maurice. 



7>/>^.— Phila. Acad. Coll. 



Horizo7i. — Claiborne Eocene. 



Specime7is figured. — Paleont. Museum Cornell Univ. 



Locality. — Claiborne, (sand bed) Ala. 



Corbula smithvillensis Harris, PI, 57, Figs. 10-17 



C. aldrichiv2x. smithvillensis Har. , Proc. Phila. Acad. Nat. Sci., 1895, 

 p. 52, pi. 3, fig. 5, a. 

 C. rugosa Heilp. , non L,am., Proc. Phila. Acad. Nat. Sci., 1890, p. 401, 

 C. {Cuneocorbula) gregorioi Dall, non Cossm., Trans. Wag., Ill, 1895, 

 p. 843. 



Harris^ original characterization. — The variety is larger than the 

 typical form, the beak in the left valve more nearly central ; right valve 

 proportionally higher ; radiating lines generally obsolete. 



It is very difficult for the present writer to undersand how 

 Heilprin could have confounded this form with rugosa Lam. or 

 how Dall could have regarded it as Cossrao.rxQ' % gregorioi. 



The umbones of the valves in smithvillensis are generally 



