133 St. Maurice and Claiborne Pelecypoda 123 



Diam. .6, Length i.i, Breadth i.i of an inch. 



Observations. Single valves of two individuals only have come into 

 my possession. Its orbicular form and beautiful concentric striae distin- 

 guish this species. In these two specimens there are no marks of growth 

 except near to the margin, where, on one specimen there are four, on the 

 other seven. These cause a thickening of the margin. 



We quite agree with de Gregorio and Dall that Conrad's de- 

 scription is too imperfect to be used in identifying this form. Had 

 he even mentioned the size of the shell it would have helped 

 wonderfully in its identification. 



Types. — No. 5152 is the type of the left valve figured by 

 L,ea. The right valve used in figuring is missing. 



Horizon. — Uppermost Sabine-Claiborne Eocene. 



Specimens figured. — Paleont. Museum Cornell Univ. from 

 Claiborne. 



Localities. — Hatchetigbee Bluff, Claiborne, Ala. 



Corbis claibornensis Dall, PI. 40. Figs. 3, 4. 



C. lai)ieUosa Con., non. Lam. Foss. Sh. Tert. Form, 1833, p. 41, Har- 

 ris' Reprint, pi. 19, fig. 5. 

 C. laniellosa Con., Amer. Jour. Sci., vol. i, 1846, p. 401, pi. 4. fig. 16. 

 Gafrariinn liratuin Con., Amer. Jr. Conch., vol. i, 1865, p. 9. 

 C. claibornensis Dall, Trans. Wag., Ill, 1903, p. 1393. 



Conrad, though referring this form to lamellosa Lam. in 

 1833, gave a short description which runs as follows : 



Elliptical, cancellate, with elevated, concentric, remote laminae ; 

 interstices with crowded, regular, transverse striae ; inner margin crenu- 

 lated. 



In 1846 he still referred it to the Paris Basin species, re- 

 marking : 



The extreme scarcity of this shell at Claiborne is remarkable, as it is 

 very abundant in the Paris Eocene. It varies little from the Paris speci- 

 mens, the principal difference being in the thicker and more approximate 

 ribs towards the base. 



Conrad evidently concluded some time before 1865 that the 

 American and European forms were specifically distinct, for in 



