54 THE PHYSICAL FEATURES OF PEIXCE GEORGE'S COU:SfTY 



Ward, Lester F. Evidence of Fossil Plants as to the Age of the 

 Potomac Formation. 



Amer. Jour. Sci., 3d ser., vol. xxxvi, 1888, pp. 119-131. 



From an examination of the fossil plants of the Potomac formation the 

 author states that "the Potomac flora, viewed in all its bearings, cannot be 

 said positively to negative the reference of the formation to the Jurassic 

 upon the evidence of the plants alone." 



is.sii. 



Bryax, O. X. The Cretaceous Formation of Southwestern Marv- 

 land. 



Amer. Nat., vol. xxiii, 1889, pp. 713-714. 



The Eocene and Cretaceous deposits in the vicinity of Fort Washington 

 and Piscataway are briefly described and are said to be underlain by a lower 

 formation which is thought to be of Jurassic age. 



Clark, Wm. B. Discovery of Fossil-Bearing Cretaceous Strata 

 in Anne x'Vrundel and Prince George Counties, Maryland. 



Johns Hopkins Univ. Circ, No. 69, vol. viii, 1889, pp. 20-21. 



Fossiliferous Cretaceous strata are reported to occur in tributaries of the 

 Patuxent River due east of Collington and at Fort Washington. Lists of 

 fossils found at these places are given. This is the first mention of fossilif- 

 erous Cretaceous strata west of Chesapeake Bay. The beds are said to lie 

 nearly horizontal. 



Fontaine, W. M. Potomac or Younger ]\[esozoic Flora. 



Monograph U. S. Geol. Surv., vol. 15, Washington, 1889, 377 pp., 180 pis. 



Contains a description of the Potomac deposits and the plant remains found 

 in them. Many of the fossils were obtained in Prince George's county at 

 Fort Washington, Beltsville and Contee and in the District of Columbia. 



Knoweton, F. H. Fossil Wood and Lignites of the Potomac 

 Formation. (Bead before Amer. Assoc. Adv. Sci., 1888.) 



Amer. Geol., vol. iii, 1889, pp. 99-106. 



A brief description is given of the Potomac formation. Good exposures 

 containing lignite and silicified wood are said to occur at Fort Washington, 

 in the cities of Baltimore and Washington and at several points in Virginia. 

 Detailed descriptions of the silicified wood and lignite are given. 



Knowetox, F. LI. Fossil Wood and Lignite of the Potomac For- 

 mation. 



Bull. U. S. Geol. Surv. No. 56, Washington, 1889. 



Contains a brief discussion of the distribution of the Potomac deposits and 

 a detailed description of some species of fossil wood found in them. 



