186 THE COASTAL PT.ATN FORMATIONS OF CECIL COUNTY 



trade 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 clav to the 

 underlying Miocene is again obscure, but indications point to an un- 

 conformity. 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 Pliocene is again unfortunately obscure. 

 At the localities just described no animal remains have been discov- 

 ered, 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 still remain to be mentioned, Cornfield Harbor, and its 

 companion deposit exposed five and a half miles south of Cedar Point 

 on the Bay shore. Conrad was well acquainted with these deposits 

 and to the former he devoted special 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 unconformity on the Miocene is beautifully shown at 

 the base of the Bay shore section. A number of fossils have been 

 described from the Cornfield Harbor locality, among which are Ostrea 

 virginica Gmelin, Area ponderosa Say, Area transversa Say, Venus 

 mercenaria Linn., My a arenaria Linn., Pliolas costata Linn., Crepi- 

 dula plana Say, Natica duplicata Say, Busycon carica Gmelin. In 

 this exposure the lower four feet of clay carries the marine forms 

 and above this there are two feet of sandy clay literally packed with 

 Ostrea virginica. These same general relations hold for the similar 

 deposits south of Cedar Point. 



The stratigraphic relation of these lenses of clay which are surely 

 unconformable on the underlying formation and apparently so with the 

 overlying sand and loams of the Talbot formation is a problem which 



