MARYLAND -GEOLOGICAL SURVEY 19.1 



in the Conococheague limestone as far north as the Eeading area of 

 Pennsylvania. They both occur in the Hoyt limestone near Saratoga 

 Springs, New York. 



Collections. Maryland Geological Survey, U. S. National Museum. 



CRYPTOZOON STEELI Seely 



Plate XXXIV, Fig. 1 



Cryptozoon steeli Seely, 1906, Kept. State Geol. Vermont, vol. v, p. 161, 

 pis. xxxiv, xxxvi, xliii, fig. 1. 



Description. The Beekmantown rocks of New York, Vermont^ and 

 northward into Canada contain a species of Cryptozoon several inches to 

 a foot in diameter which differs from the other species of the genus in 

 that the organism is usually made up of a single globular or hemispherical 

 mass of lamellae. The successive layers are quite parallel and arranged 

 concentrically even in the largest specimens. These layers are composed 

 of a dense material apparently without definite organic structure. 



In the Cumberland Valley this particular form of Cryptozoon is 

 apparently restricted to a definite zone in the Lower Beekmantown. As 

 the fossil weathers out in large, silicified masses accompanied by much 

 platy chert, this zone is generally easily recognized. Cryptozoon steeli 

 therefore forms an excellent guide fossil in mapping, as it not only 

 assists in the recognition of the strata, but the chert masses accompanying 

 it indicate the outcrops of this zone. These, if plotted, help to decipher 

 the geological structure. The Cryptozoon steeli zone of chert has been a 

 most valuable aid in determining the structure of the Beekmantown in 

 the Valley west of the Martinsburg shale belt where frequently lack of 

 rock outcrops has caused great difficulty in mapping. 



Occurrence. BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). 

 In the Appalachian Valley of Maryland and southern Pennsylvania 

 this is a cbmmon fossil about 800 feet above the base of the Beekmantown. 

 Numerous specimens may be found among the residual cherts of this 

 zone at practically every outcrop both east and west of the Martinsburg 

 shale belt of Maryland, particularly in the vicinity of Hagerstown. 



Collections. Maryland Geological Survey, U. S. National Museum. 

 13 



