.MAHYI,.\NI) CKOI.OOICAL SURVKY 01 



crilcriri lor llio brdjid coriclation of tlio deposits, llu.-ir iiioro r-xiiot par- 

 iillflisiii hciiiff (lolfniiincd (Ui other and more definite /.'rounds. 



European Equivolenls. 



Several attempts have been made to coiTelate the deposits of the 

 Middle Atlantic Slope with those of Europe. The earlier attempt.s in 

 this direction are presented in the Historical Keview. Most of the con- 

 clusions reached were based on very insufficient data, the faunas beinrr 

 inadequately studied and even the sequence of depo.«its not being in 

 niost instances fully understood; but even after Conrad ' began his study 

 of the Maryland Tertiaries and described more or less fully the rich 

 faunas contained therein, his correlations were still based on very insuf- 

 ficient knowledge. As the result of his investigations, he correlated 

 the Eocene deposits of ^Maryland with the London Clay of En^rland and 

 the Calcaire Grassier of France. 



Lyell,' during his visit to America in 1841, examined somewhat hur- 

 riedly the Eocene deposits of the Middle Atlantic area, hut attempted no 

 detailed correlation, stating, however, that the Tertiary formations which 

 he saw " agree well in their geological types with the Eocene and 

 Miocene beds in England and France." 



Heilprin," in an important publication on United States Tertiary 

 Geolog}', discusses the equivalency of the European and American Ter- 

 tiary formations. In a chapter dealing with " A Comparison of the 

 Tertiary Mollusca of the Southeastern United States and Western Europe 

 in Eelation to the Determination of Identical Forms," he refers to the 

 species which Conrad, Lea and Meyer had regarded as analogous to Euro- 

 pean forms, and also discusses in detail all those species which he regards 

 as the same or which have certain points of resemblance. Eeferring to 

 the more important of these forms in an earlier portion of the same 

 volume (p. 13) he says: '"If such comparisons are of any value strati- 

 graphically, we may fairly look upon the Maryland J^ocene deposits — the 



'Jonr. Acad. Nat. Sci. Pliila., vol. vi, 18:^.0, pp. 205-217; Fossil Shells of the 

 Tertiary, 1832, pp. iv, 0, 12, 13. 



-Proc. Geol. Soc. London, vol. iv, 1S45, pp. .56.3-564; C2uart. Jour. Geol. Soc. London, 

 vol. i. 184.5, p. 429-430. . 



'Contributions to the Tertiary Geology and Paleontology of the United States, 

 pp. ^3-101. 



