Observations on the Eocene deposits of the United States. 



1 In a preceding No. of this work, (page 28) I alluded to a de- 

 posit of large oyster shells in South Carolina and Georgia, which 

 Mr. Finch has termed Calcaire Ostree*, believing that it constitu- 

 ted a distinct formation, not referrible to any particular period in 

 the scale of European deposits.' I have since visited a portion 'of 

 the southern States, and cdn say, from personal observation, that 

 the continuous bed of oyster shells described by travellers and 

 others, includes, in fact, two; distinct formations, one of seconda- 

 ry, the other of tertiary origin, and that two distinct species of 

 Ostrea have been confounded' with that "finger post" of the creta- 

 ceous strata, Exoyyra coststa, Say.f These three shells combined 

 constitute that anomalous species called Ostrea gijantissima by 

 Mr. Finch. Upon this supposed species was erected the formation 

 termed Calcaire Ostree, which we have proved to be no more than 

 the creation of Mr. Finch's imagination ; yet a traveller ignorant 

 of the generic or specific character of the shells alluded to, would 

 be likely to arrive at the same conclusion with that geologist and 

 suppose that a continuous deposit, characterized by a single spe- 

 cies of Ostrea, extended from South Carolina to the Mississippi 

 river. Of the two species of Ostrea mentioned above, the O. sel- 

 Iwformis characterizes a peculiar stratum of the Eocene at Clai- 

 borne, and is also found in the newer cretaceous strata of South 

 Carolina. The 0. (teoryiana, (nobis) which much resembles O. 

 lonyirostris, Lam. is characteristic of the Eocene strata at Shell 

 Bluff on the Savannah river; near Milledgeville, Georgia, and at 

 Orangeburgh, South Carolina. 



The Eocene first appears at Upper Marlborough, in Prince George 

 county, Maryland. The upper stratum is an indurated arenaceous 

 marl about 4 feet thick, replete with casts of shells, most of which 

 are identical with species common at Claiborne, Alabama. Beneath 



*Americun Journal of Science and Arts, vol. VII. p. 39. 



fin Dr. Goldfuss' splendid work, "Pctrifacten", we observe the genus Exo- 

 gyra is credited to Sowerby, whereas, our late and lamented naturalist, Thomas 

 Buy, Es<j. instituted it, and we consider it' one of his happiest efforts in the sub- 

 division of genera, presenting us with an extremely interesting and natural 

 group of shells characteristic of Cretaceous strata, which were previously refer- 

 red to Chaina by European conchologists. 



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