44 THE PHYSICAL FEATURES OF PRINCE GEORGe's COUNTY 



1853. 



Marcou^ Jules, A Geological Map of the United States and the 

 British Provinces of l^orth America, with an explanatory text, (etc.) 

 8vo. Boston, 1853. 



Shows the general distribution of the Coastal Plain strata. No Cretaceous 

 represented on the Western Shore of Chesapeake Bay, 



1855. 



Marcou^ J. Resume explicatif d'un carte geologique des Etats- 

 Unis et des provinces anglaises de I'Amerique. 



Bull. Soc. Geol. France, 2nd ser., tome xii, 1855, pp. 813-936. Colored 

 geological map. 



Mention is made of the occurrence of Eocene at Fort Washington and brief 

 statements concerning the Cretaceous and Tertiary deposits of the entire 

 State. 



1856. 



Bailey^ J. W. On the Origin of Greensand, and its formation in 

 the oceans of the present epoch. 



Amer. Jour. Sci., 2nd ser., vol. xxii, 1856, pp. 280-284. 



Proc. Bost. Soc. Nat. Hist., vol. v, pp. 364-368. 



Reference is made to the abundant casts of Polj/thalamia in the Eocene 

 greensand of Fort Washington. 



Ehrenberg, C. G. Zur Mikrogeologie. 

 Two vols, and atlas, royal folio, 41 pis. Leipzig, 1854-56. 

 Mention forms of protozoa from Fort Washington. 



1859, 



Johnston,. Christopher. jSTotes on Odontology. 

 Amer. Jour. Dental Sci., Phila., n. s. vol. ix. No. 3, 1859, pp. 337-343. 

 A description is given of Astrodon (afterwards called Astrodon jolurstoni) 

 from Bladensburg. 



1860. 

 Tyson, Philip T. First Report of Philip T. Tyson, State Agri- 

 cultural Chemist, to the House of Delegates of Maryland, January, 



