46 THE PHYSICAL FEATURES OF PRINCE GEORGE S COUNTY 



1865. 



CoNRAD^ T. A. Observations on the Eocene Lignite Formation of 

 the United States. 



Proc. Acad. Nat. Sci., Phila. vol. xvii, 1865, pp. 70-73. 



(Abst). Amer. Jour. Sci., 2d ser., vol. xi, 1865, pp. 265-268. 



The lignitic beds now included in the Magothy formation are considered 

 to constitute the basal beds of the Eocene, and are correlated with the 

 Ijondon clay of Eui'ope. "They reveal a singular state of the globe at the 

 commencement of the Tertiary period, presenting a vast level region covered 

 by a dense forest, in which palms and oaks grew side by side, interspersed 

 with lakes and rivers, and long shallow bays of salt water penetrating to 

 the interior of the continents. This state of the globe was exhibited in 

 l^Jurope and America at the same time." p. 268. 



Conrad, T. A. Catah^gne of the Eocene and Oligocene Testacea 

 of the United States. 



Amer. Jour. Conch., vol. i, 1865, pp. 1-35. 



Several species of Eocene fossils from Upper Marlboro and Piscataway 

 Creek are included in the lists. 



Leidy, Joseph. Cretaceous Reptiles of the United States. 

 Smith. Contrib. to Knowledge, No. 192, vol. xiv, 1865, 135 pp., 20 pis. 

 Teeth of Astrodon johnstoni found in an iron ore bed near Bladensburg, 

 are described and figured. 



1866. 



Conrad, T. A. Check List of the Invertebrate Eossils of Xorth 

 America (Eocene and Oligocene). 



Smith. Misc. Coll., vol. vii, 1866, 41 pp. 



Lists of all Eocene and Ohjocene fossils known at that time are given but 

 without exact locality references. The Eocene deposits near Washington, at 

 Piscataway, and at Upper Marlboro are referred to the Lower Eocene. 



1867. 



HiGGiNS, James. A Succinct Exposition of the Industrial Ee- 

 sources and Agricultural Advantages of the State of Maryland, Svo, 

 109+iii pp. 



Md. House of Delegates, Jan. Sess.,-1867. [DD.] 



Md. Sen. Doc, Jan. Sess., 1867. [U.] 



Contains a description of the soils and physiographic features of each of 

 the counties of the State. 



