444 PROCEEDINGS OF THE ACADEMY OF [1881. 



NOTE ON THE APPROXIMATE POSITION OF THE EOCEIJE DEPOSITS OF 



MARYLAND. 



BY ANGELO IIEILPRIN. 



The positive determination of the relation which the older 

 Tertiary deposits of Maryland — those of Ft. Washington, near 

 the City of Washington, and Piscatawa}^ and Upper Marlborough 

 in Prince George's County — hold. to the typical American Eocene 

 series as exhibited in Alabama, can only be arrived at when a 

 direct stratigraphical continuity can be traced between the 

 deposits of the two states, or between their previously recognized 

 representatives in the intervening states. This is due to the fact 

 that several members of the Eocene series appear to be absent 

 from this portion of the Atlantic border, but exactly which it has 

 as yet been impossible to determine. The presence of strata of 

 Jacksonian age has never been detected, nor have we an}' positive 

 knowledge concerning the existence in the State of any beds which 

 maybe looked upon as the equivalents of the Orbitoide limestone, 

 although Oligocene (Vicksburgian) strata may exist along the 

 Chesapeake. But whether the deposits in question — Ft. Wash- 

 ington, Piscataway, and Upper Marlborough — represent the 

 Cl:iibornian,Buhrstone,or Eo-Lignitic is a matter of considerable 

 uncertainty, perhaps largely due to their comparatively feeble 

 development. Almost the onl^' evidence we have bearing upon 

 this point is derived from the character of the contained fossils, 

 but even here the results obtained are far from satisf^ictor}^, and 

 for two reasons: in the first place, the charpcter of the Eocene 

 fossils is largely uniform throughout the greater portion of the 

 entire series, as is shown by nearly the lowest and highest 

 exposures in the State of Alabama ; and in the second place, the 

 great distance intervening between the two localities — Alabama 

 and Maryland — may readily account for certain differences in the 

 general aspect of the two fossil faunas, which otherwise would 

 probably be attributable to a non-contemporaneity in the periods 

 of their introduction. The evidence afforded by lithological char- 

 acters is almost equall}'^ unsatisfactory, since there is a frequent 

 repetition of the general rock aspect — green sands, clays, and 

 siliceous marls — observable at different stages of the series. 

 Conrad, the only investigator whose observations on this subject 



