MARYLAND GEOLOGICAL SURVEY 9 ( J 



doubted Talbot ago, which extend upward to the top of the cliff. Al- 

 though the base of this lignitic clay series is buried beneath beach sands, 

 field relations lead to the conclusion that it is very much younger than 

 the Miocene clays on which it rests unconformably. 



A similar section is to be seen on the Patuxent river, about a mile below 

 Sellers Landing. Large stumps here protrude from a dark, basal clay 

 bed, some five feet in thickness, which is covered by three feet of sand, 

 and this again is buried beneath ten feet of Talbot sand and gravel. The 

 relations of the basal clay to the underlying Miocene is again obscure, but 

 indications point to an unconformity. Another section is exposed along 

 the shore one and one-half miles northwest of Cedar Point, where a thin 

 bed of drab clay carrying vegetable remains is overlain abruptly with 

 sands and gravels. Its contact with the Miocene is again unfortunately 

 obscured. At the localities just described no animal remains have been 

 discovered, but on the north bank of the Potomac, about half way between 

 St. Mary's river and Breton Bay, there is a deposit of lead-colored clay, 

 exposed for a quarter of a mile along the shore. It is buried at each end 

 as well as above by sands and gravels and carries both lignite and 

 Gnathodon cuneata Conrad. Although the description given by Conrad 

 is somewhat vague, it is highly probable that he visited this locality and 

 collected specimens of the fossils. Two more localities should be men- 

 tioned, Wailes Bluff, near Cornfield Harbor, and its companion deposit 

 exposed at Langleys Bluff five and a half miles south of Cedar Point on 

 the Bay shore. Conrad was well acquainted with these deposits and 10 

 the former he devoted especial attention. Each is about ten feet thick, 

 occurs at the base of a low cliff, is composed mostly of a dark, lead-colored 

 clay, and is overlain abruptly with Talbot sand and gravel, while uncon- 

 formity with the Miocene is beautifully shown at the base of the Bay 

 shore section. A number of fossils have been described from the Corn- 

 field Harbor locality, among which are Ostrea virginica Gmelin, Area 

 ponderosa Say, Area transversa Say, Venus mercenaria Linne, Mya 

 arenaria Linne, Barnea costata (Linne), Crepidula plana Say, Tolynizes 

 duplicatus (Say), Fulgur carica (Gmelin). In this exposure the lower 

 four feet of clay carries the marine forms and above this there are two 



