THE SECTION AT SCHOHARIE, N. Y. 363 



equivalent of the Clinton, is somewhat variable in color, weathers 

 dirty white and contains much nodular pyrite accompanied by 

 barite. The same characteristics appear at Howe s cave, five 

 miles west from Schoharie. The pyrite was mined near Scho- 

 harie thirty years ago, but the venture proved unprofitable. 

 The exposures at Schoharie are incomplete but the thickness 

 cannot exceed thirty feet. 



There is here a veiy striking contrast with the section of south- 

 ern Pennsylvania and of other localities farther southward. 



The Hudson shales, in Evitts mountain, Bedford county, Penn., 

 mostly yellow in color, contain some sandstones near the top, 

 where the color changes and physically there is a gradual passage 

 to the lower or red Medina. Rafinesquina alternafa, Plectain- 

 bonites sericca, RJiynchotrema capax and Leiopteria radiata pass 

 upward into the red Medina. The conditions in southwestern 

 Virginia are the same. On the northern side of Big Walker 

 mountain in Bland county, near Sharon Springs, as well as in 

 Lyons gap through the same mountain in Smyth county and Hay- 

 ter's gap through Clinch mountain in Russell county, exposures 

 are especially good, as they show a fossiliferous bed at about one 

 hundred feet below the white Medina, in which RJiynchotrema 

 capax, Actinopteria cmacerata, Leiopteria radiata, a Modiolopsis 

 a large linguloid form and fragments of Orthoceras occur abund- 

 antly. The Oneida seems to disappear in south-central Penn- 

 sylvania and thence southward the ^passage from Ordovician to 

 Silurian is gradual at most of the exposures. 



THE NIAGARA 



The Niagara limestone is represented by the Coralline lime- 

 stone of the older reports, which, at the complete exposure on 

 Schoharie river above the bridge, is a massive rock in three layers ^ 

 averaging in all six feet. The upper portion is very dark on fresh 

 surface, the lower portion less so, but both weather light gray. 

 This limestone is well exposed along the west side of the river 

 for an eighth of a mile above the bridge and at several points 

 below the bridge ; it can be followed easily to Howe's cave, 



