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ART. IX. — Observations on the Eocene formation, and descriptions of one hundred 

 and five new fossils of that period, from the viciyiity of Vicksburg, Mississippi ; 

 with an Appendix. By T. A. Conrad. 



Ill the Spring of 1845, I collected about one hundred and nine species of Eocene 

 fossils, most of which appear to be new species. There are sixty univalves, forty -two 

 bivalves, one multivalve shell, and six or seven polyps. 



Of these fossils, I can identify two only with species of the Claiborne sands; 

 Inftindibulum trochiformis and Conus saurodens. Very few others are related to 

 species of the Alabama sand strata. Lucina Missis sippiensis, Sigaretus Mississippiensis 

 and Dentalium Mississippiensis, are the only shells which might be confounded with 

 species of those deposits. 



The Vicksburg group contains three species of bivalves which have mucli 

 resemblance to Miocene fossils of this country. Lima staminea approaches X. 

 papyria; Corhula engonata is allied to C. inequalis, Say ; and Nuciila VicJcsburgensis, 

 to N. obliqua, Say. 



I have not observed a recent species in this group, and yet it is decidedly more 

 modern than that of the Claiborne sands ; and as both deposits have but two species 

 in common, I thought it advisable to designate the former, Upper or Newer Eocene, 

 and the latter Lower or Older Eocene, as the two divisions are more distinct than 

 the Older and Newer Pliocenes. 



In the American Journal of Science and Arts, I have given a sketch of the 

 Mississippi Eocene, and observed that not* more than ten species would be found, 

 on comparison, identical with Claiborne shells. I had reference to the sand at 

 Claiborne, and not including the limestone above it. A careful comparison has 

 reduced the number to two species, for the Dentalium, which, when at Vicksburg 

 (without a Claiborne specimen for comparison) I had supposed to be D. ihalloides, is 

 a distinct, though closely allied species. 



This newer portion of the Eocene in Mississippi is represented in Alabama by the 

 white limestone at St. Stephens on the Tombeckbe river, and the similar rock which 

 constitutes the uppermost stratum at Claiborne, on the Alabama river ; all being 

 admirably connected by the abundance of Nummulites Mantelli. There is a similar 

 limestone, in Charleston county, South Carolina, in which I found Scutella J,yelli and 

 Pecten calvatus, fossils of the Claiborne limestone, and both rocks are probably of the 

 same geological age. The limestone of Tampa Bay, Florida, is included in the 



* 111 the paragraph alluded to. this word was accidentally omitted. I did not when it was written suppose that 

 ten fossils would be found to correspond with species of the Claiborne sands. 



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