35 



dita planicosta is in great abundance, but does not attain to one half 

 the size of specimens common in tbe sand. 



The insulated position of the Eocene at Claiborne, is remarkable ; 

 west of the vicinity of the village, the whole country is secondary, 

 or of that limestone which Dr. Morton has compared to the Maes- 

 tricht deposit, and termed the " upper division of the cretaceous 

 group". As we proceed west, we traverse hills of the same lime- 

 stone but find no trace of the tertiary until we arrive at St. Stephens, 

 on the Tombeckbe, where it is still more isolated than at Claiborne, 

 being bounded immediately from the river by the cretaceous strata 

 on the west, and on the south by alluvium which intervenes between 

 it and the secondary. On the north it also dips under the alluvium, 

 and appears to be the rock which forms the rapid two miles north of 

 St. Stephens, the first which is met with in ascending the river. The 

 tide flows to the foot of this rapid, a distance of ninety miles from 

 the head of Mobile Bay, but this happens only in the lowest stage of 

 the water. 



From some notices which have been published respecting the ele- 

 vated bluff at Natchez, on the Mississippi, we infer that is of the 

 formation in question, which, crossing the river, reappears on the 

 bank of the Ouachita, near the town of Monroe, in Louisiana, where 

 it is associated with creatceous strata. Th'is locality is of great 

 interest to a geologist, as it will, when investigated, solve a problem 

 of great importance, whether or not remains of animals belonging to 

 the order Enalio-Sauri exist in the tertiary. The gigantic vertebra? 

 of the Bdsilosanrus, (Harlan) were found here enveloped in Eocene 

 marl, but specimens which Dr. Harlan conceives to be relics of the 

 same species, from the newest secondary limestone of Clark county, 

 Alabama, have been sent to this city by John G. Creagh, Esq. and 

 A. B. Cooper, Esq. of Claiborne. These highly interesting remains 

 were found on the plantation of Mr. Creagh, and are now in the pos- 

 session of Dr. Morton, who has laboured diligently to procure what- 

 ever may advance a knowledge of American geology. 



In Wilcox county, Alabama, on the plantation of my friend Judge 

 Tait, the Eocene appears in the form of a dark coloured sandstone, 

 in which the shells are only traced by imperfect chalky vestiges, 

 but sufficiently defined to shew their relation to the fossils at Clai- 

 borne. The common grist mills of the vicinity are supplied with 

 stones from this rock, which I have not seen in situ, nor do I know 

 the extent to which it has been observed in Alabama. In the de- 

 composed state of the fossils,- it differs from other varieties nearly 



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