40 THE PHYSICAL FEATURES OF PRIXCE GEOKGe's COUNTY 



DucATEE,, J. T. Outline of the Physical Geography of Marylainl, 

 embracing its prominent Geological Features. 



Trans. Md. Acad. Sci. and Lit., Vol. I, Pt. I, 1837, pp. 24-54, with map. 



A general description of the physiography and geology of the entire State 

 is given with many details of local features. It is a general summary of 

 information previously published in various places. Mention is made of the 

 covering of boulders and coarse gravel near the inner edge of the Secondary 

 (Cretaceous) rocks while farther out the sands and clays of the Secondary 

 and Tertiary formations are uncovered. 



1S38. 

 Conrad, T. A. Fossils of the Medial Tertiary of the United 

 States. 'No. 1, 1838. [T3escription on cover 1839 & '40.] 32 pp. 

 Plates I-XVII. 



Republished by William H. Dall, Washington, 1893. 



A general description of the distribution and characteristics of the Miocene 

 of the Atlantic Coastal Plain is given. The Miocene is called the Medial 

 Tertiary or Older Pliocene and the Eocene is called Lower Tertiary. The 

 Medial Tertiary is said to overlie the Lower Tertiary at Upper Marlboro and 

 is found to the south of a line drawn from Annapolis to Fort Washington. 



1839. 

 Conrad, T. A. !N"otes on American Geology. Observations on 

 Characteristic Fossils, and upon a fall of Temperature in different 

 Geological Epochs. 



Amer. Jour. Sci., vol. xxxv, 1839, pp. 237-251. 



"At Upper Marlborough and Piscataway, in Maryland, a deposit of the 

 Eocene period occurs, composed of the detritus of green sand, a material 

 originating in the cretaceous epoch. One fossil of the latter formation, 

 {Gryphaea vomer, [ostrea lateralis, Wilson]) is not uncommon among the 

 Eocene fossils. This is at the same time the lightest and most indestructible 

 of the cretaceous shells, and therefore the one most likely to be carried 

 unbroken with the detritus of the green sand." 



1842. 



Conrad, T. A. Descriptions of Xew Tertiary Fossils. 

 Second Bull. Proc. Nat. Inst. Prom. Sci., 1842, pp. 192-194, 2 pis. 

 Plioladomya marylandica is described from Piscataway. 



