34 , : 



of fossils are common to the two latter ; facts just the reverse 

 of those which have been published in relation to the secondary 

 and tertiary of Europe. No vestiges of fresh water shells are ob- 

 served in our Eocene, and I conclude, from the general character 

 of the fossils, that the formation, unlike that of Paris, has not 

 been of estuary but oceanic origin. M. Deshayes informs us that 

 137 species of Cerithium occur in the Paris basin, and this is said 

 to be a genus partial to estuaries. . At Claiborne only three spe- 

 cies occur ; one is rare and a doubtful member of the genus> and 

 of the other two species I procured but one specimen of each, 

 which, tends- to prove that they were not in a situation favourable 

 to their increase. The stratum of oysters beneath may have been 

 deposited in a lagoon, but if so, the ocean must have returned and 

 brought back the same class of shells, which originated in the first 

 bed of the Eocene sea, whilst with this convulsion the Ostrea sel- 

 he for mis entirely disappeared, and at the same time was depos- 

 ited the debris of some rock which then first mingled with the 

 testacea ; and as this stratum of sand and shells is only about four- 

 teen feet thick, it was probably soon formed, comparatively speak- 

 ing, which will explain the cause why so few species of testacea 

 occur in comparison with synchronous deposits- in Europe. 



The following species of the Eocene at Paris occur also in the 

 sand at Claiborne: Solarium patulum, (Lam.) S. canaliculatum, 

 (Lam.) Bulimus terebellatus, (Lam.) Sigaretus canaliculatits, 

 (Sow.) Calyptrea trochiformis, (Lam.) Pyrula tricarinata, (Lam.) 

 Acicula trigona, (Lam.) Cytherea erycinoides, (Lam.) C. subery- 

 cinoides, (Desh.) Corbis lamellosa, (Lam.) Cardita planicosta, 

 (Blain.) Fistulana elongata. (Desh.) 



8. A mass of Ostrea selheformis, about three feet in thickness, 

 in sand cemented by carbonate of lime. As this oyster also oc- 

 curs in the newer Cretaceous strata, at first I supposed the present 

 to be of the same age . as the latter deposit, but a subsequent ex- 

 amination of the inferior stratum convinced me to the contrary, 

 as I found it characterized by Eocene fossils exclusively. Large 

 specimens of the Ostrea generally have a water worn appearance, 

 and occur mostly in single valves ; the young which are vastly 

 abundant are also disunited, but invariably uninjured and unworn. 

 Fragments of this rock form a talus at the base of the escarpment. 



4. A dark colored marl, seventy feet in thickness, in which the 

 same Ostrea occurs, but smaller and less abundant than above. 

 Other fossils are very rare, but I found a specimen of Playiosto- 

 ma dumosum, (Morton) which had attached itself while living to 



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