52 THE PHYSICAI. I-EATURES OF TRINCE GEOKGe's COUXTY 



White, I. C. Rounded Boulders at High Altitudes along some 

 Appalachian Rivers. 



Amer. Jour. Sci., 3d ser., vol. xxxiv, 1887, pp. 374-381. 



"Submergence, with re-elevation in comparatively recent times, will then 

 give a sufficient explanation for the existence of the elevated bowlder deposits 

 in the vicinity of Washington, D. C, Richmond, Philadelphia, and possibly as 

 far west as Cumberland." 



1888. 

 Clark^ Wm. B. On three Geological Excursions made during the 

 months of October and November, 1887, into the southern counties 

 of Maryland. 



Johns Hopkins Univ. Circ, No. 63, vol. vii, 1888, pp. 65-67. 



The following fossils are reported from the Eocene at Fort Washington: 

 Cucullaea gigantea, Conrad; Crassatella, sp.; Cytherea, sp.; Cytherea (Dosini- 

 opsis) Meekii, Conrad; Turritella Mortons, Conrad; Sharks teeth at Upper 

 Marlboro a green and yellow variegated marl containing casts or fragments 

 of several genera of mollusca is said to be well exposed. 



Knowltojst^ F. H. The Fossil Lignites of the Potomac Formation. 

 Proc. Amer. Assoc. Adv. Sci., vol. xxxvii, 1888, pp. 206-208. 

 The characteristics and mode of occurrence of the lignitized and silicified 

 plant remains of the Potomac formation are briefly described. 



Marsh, O. C. iSTotice of a jSTew Genus of Sauropoda and other 

 new Dinosaurs from the Potomac Formation. 



Amer. Jour. Sci., 3d ser., vol. xxxv, 1888, pp. 89-94, figs. 1-9. 



The remains of three new species of herbivorous and two new species of 

 carnivorous dinosaurs obtained from the Potomac strata of Prince George's 

 county are described and figured. The author states that the fossils are 

 "apparently of Upper Jurassic age, but quite distinct from any hitherto 

 discovered in this country." 



McGee, W J. The Geology of the Head of Chesapeake Bay. 



7th An. Report U. S. Geol. Surv. Washington, 1888, pp. 537-646. 



Abst. Amer. Geol., vol. i, 1887, pp. 113-115. 



Contains a general discussion of the Potomac and Columbia deposits. 

 Evidence is given to prove recent displacements in the vicinity of the "fall 

 line." At Washington the total displacement is from 75 to 100 feet. 



