48 THE PHYSICAL FEATURES OF PRINCE GEOKGE^S COUNTY 



1880. 

 IIeilprin, Angelo. On the Stratigrapliical Evidence Afforded Ly 

 the Tertiary Fossils of the Peninsula of Maryland, 

 Proc. Acad. Nat. Sci., Phila., vol. xxxii, 1880, pp. 20-33. 

 After a careful examination of the fossils found along the Patuxent, Chop- 

 tank and St. Mary's rivers and the Calvert Cliffs, the author proposes the 

 separation of the Miocene into the Older and Newer periods. The beds at 

 Fair Haven are typical Older Miocene and the St. Mary's lower Patuxent, and 

 Choptank river beds belong to the Newer Miocene. 



1881. 



Heilpin, Angelo. ISTote on the Approximate Position of the 

 Eocene Deposits of Maryland. 



Proc. Acad. Nat. Sci., Phila., vol. xxxiii, 1881, pp. 444-447. 



The Eocene of Maryland, consisting of "the Piscataway sands below, and 

 the Marlborough rock above" is supposed to represent "a horizon nearly equal 

 to that of the Thanet sands of England and the Bracheux sands of the Paris 

 basin, or of the British Bognor rock (i= London Clay)" are also correlated 

 with the Alabama deposits. They are supposed to be equivalent to the beds 

 "near the base of the 'Buhrstone' or possibly even lower." (p. 447.) 



1882. 

 Heilprin, Angelo. On the relative ages and classification of the 

 Post-Eocene Tertiary Deposits of the Atlantic Slope. 



Proc. Acad. Nat. Sci., Phila., vol. xxxiv, 1882, pp. 150-186. 



(Abst.) Amer. Jour. Sci., 3d ser., vol. xxiv, 1882, pp. 228-229. 



Amer. Nat., vol. xvii, 1883, p. 308. 



From a comparison of faunas the Eocene deposits of Maryland are cor- 

 related with the Eo-Ligniter of Alabama, and the Miocene beds of the State 

 are grouped in a division called the Marylandian which is supposed to be 

 older than any other Miocene beds of this country, with the possible exception 

 of the basal Miocene beds of Virginia which may be contemporaneous. 



1883. 

 Smock, J. C. The Useful Minerals of the United States. Min. 

 Resources of the U. S., 1882. Washington, 1883, pp. 690-693. 



The following minerals are reported from this county: Limonite from 

 Snowden's Bank, Greensand and shell marls. Lignite in clay, Pyrite from 

 Oxen Creek, Siderite, Tripolite from near Nottingham. 



