Harris — Eocene Deposits of Maryland and Virginia. 301 



Aet. XXIX. — On the Geological Position of the Eocene 

 Deposits of Maryland and Virginia; by Gilbert D. 

 Harris. 



Iisr the spring of 1830,* T. A. Conrad made a visit to the 

 western shore of Maryland for the purpose of collecting fossil 

 remains and observing the geological features of the region. 

 He discovered in the vicinity of Ft. Washington beds that he 

 correlated with the London Clay of England since they con- 

 tained among other extinct species Venericardia planicosta of 

 Lamarck. A few years laterf he called attention to the resem- 

 blance of Gucidlcea gigantea of this locality to a European 

 species, and noted the similarity of Ostrea compressirostra and 

 the European Ostrea oellovacina. In the same work he de- 

 scribed many new species from Claiborne, Alabama, mentioned 

 others from Vance's Ferry, South Carolina, and classified 

 Maryland, Alabama, and South Carolina deposits alike as 

 "Middle Tertiary or London Clay and Calcaire drossier. " 



The Rogers in 1839^: differentiated this series from the over- 

 lying Miocene and underlying Cretaceous in Virginia and cor- 

 rectly referred it to an Eocene horizon and described several 

 of its characteristic species. 



Conrad, in the Proceedings of the National Institution, 

 1S41,§ mentioned many Eocene localities in the Gulf and At- 

 lantic slope States and pointed out the resemblance of the 

 Upper Marlboro rocks of Maryland to those of Bangor, Eng- 

 land, Ostrea oellovacina he affirmed was found at either local- 



Up to this time, no stress had been laid on the stratigraphic 

 position of the various Eocene outcrops in America ; to know 

 that they were Eocene was all sufficing. In 1855, however, 

 Conrad I established three subdivisions in the Alabama and 

 Mississippi deposits of this series, naming them in descending 

 order, the Vicksburg, Jackson and Claiborne groups. In 1865 

 he instituted another, the Lignite Formation,^ wherein he 

 seemingly desired to include beds lying between the " Buhr- 

 stone, " as described by Tuomey, and the Cretaceous. To this 

 formation he referred the dark colored friable clays of Piscat- 

 away Creek and the basal bed of Tuomey's section on Bashia 

 Creek, Clark Co., Alabama ; but the " Marlboro rock " to use 



* Jour. Ac. Nat. Sci. Phila., 1st Series, vol. vi, 1830, pp. 205 et seq. 



f Fossil Shells Tert. Form. N. A., Harris' Reprint, p. [21 J. 



% Trans. Am. Phil. Soc., N/. Ser., vol. v, 1839, p. 347 et seq. 



§ Second Bull , pp. 172-179. 



|| Proc. Acad. Nat. Sci. Philad., vol. vii, p. 257. 



1 Proc. Acad. Nat. Sci. Philad , vol. xvii, 1865. 



