57 St, Maurice and Claibokne Pelecypoda 57 



Leda semenoides Aldrich, Pi. 23. Figs. 5, 6. 



Lcda semenoides, Aldr., Bull. Amer. Pal., vol. i, 1S95, p. 70. pi. 6, 

 fig- 5. 



For the original description, see the above reference. Both 

 description and illustration were drawn from a very immature 

 specimen: Though this species is not rostrate in the same man- 

 ner posteriori}' as semen, (i. e. the upper, posterior radiating fold 

 alone projecting far out from the general margin of the shell) the 

 two, radiating, posterior, crenulated folds form something of a 

 beak as the figure of a cast clearly shows. The adult shell reaches 

 a length of 17 mm. at least. 



7>/^.- Aldrich Coll. J. H. Univ. Coll. 



Horizon. — St. Maurice Eocene. 



Specimens figured. — Paleont. Mus. Cornell Univ. 



Localities. — Lisbon, Hamilton Bluff, Ala.; Ft. Gaines, Ga. 



Leda COelata Conrad, PI. 23. Figs. 7, 8, 9. 



Nucula ccelata Con., Am. Jr. Sci., vol. 33, Jan. 1833, p. 343. 



Nticida brogniaHi L,ea, Cont. to Geol., Dec, 1833, p. 82, pi. 3, fig. 61. 



Leda cadata Con., Proc Acad. Nat. Sci., Phila., 1854, p. 29. 



Nuculana coelata Con., Am. Jr. Conch., vol. i, 1865, p. 13. 



Leda brofigtn'arfi de Greg., Mon. Faun. Eoc, Ala., 1890, p. 187, pi. 22, 



figs. 27-29. 

 Leda coelata Dall, Trans. Wag. &c, vol. Ill, 1895, p. 578-579. 



Conrad's original description. — Shell ovate, elongated, with irreg- 

 ular undulated ridges ; anterior submargin with three minutely crenulated, 

 carinated lines diverging from the apex ; beaks nearly central. Length, 

 half an inch. 



This species is readily identified, and the t5'pe is probably one 

 of the three specimens in the Conradian collection at the Phila. 

 Academy. 



The surface ornamentation of this species is rather unique. 

 Two to four concentric folds usually appear near the lower margin 

 of the shell ; above, towards the beaks true concentric lining is lim- 

 ited to microscopic increments of growth. However, superim- 

 po.sed on this system of ornamentation is another, appearing at 

 first sight to be concentric markings about the umbonal region, 



