376 STEVENSON 



on the fresh surface. Weathered, it resembles the Oriskany, but 

 is darker. It is so hard as to suggest that silica is the cement- 

 ing material. But the iron leads to disintegration and the rock 

 wastes away, so that its outcrop is concealed by heavy blocks of 

 Corniferous, between which debris has accumulated. The only 

 outcrop discovered is on the northwest face of West mountain, 

 but the presence of the rock is shown on both sides of the valley 

 by the fragments strewn about the fields. The unweathered 

 rock is so hard as to yield nothing to the collector, but several 

 layers are extraordinarily rich in individuals of a few types, 

 which can be procured easily from weathered fragments. The 

 ordinary forms belong to Stroplieodonta, Pciitamerella, Atr.vpa, 

 Orthoccras, Cyrtoccras, Trod loc eras and GoinpJwceras. Cephalo- 

 pods are the prevalent forms. Atrypa reticularis is the most 

 common of the brachiopods and its casts as well as those of 

 StropJieocionta are in admirable condition for study. 



The Corniferous limestone caps West mountain and the 

 schoolhouse hill on the west side of the valley and is easily 

 followed to where it passes under the river near Borst's dam, 

 about four miles abov^e Schoharie. It is quarried extensively at 

 the lime-kilns below the dam. It is imperfectly shown on the 

 east side at several places within two miles and a half above 

 Schoharie village, but, above that, the valley is eroded in Cauda- 

 Galli and the bluff is covered with debris from the Hamilton. 

 The Corniferous is known as the "Top gray limestone." It is 

 gray, brittle and contains much chert in lenses and irregular 

 layers. The older geologists divided it into Onondaga and Cor- 

 niferous, but chert appears to be characteristic of both divisions 

 and the older name should be applied to the whole. The thick- 

 ness in schoolhouse hill is not far from 30 feet but it is greater at 

 the limekilns where the whole is shown. Fossils are abundant 

 but only a few forms are likely to be obtained by the collector. 

 Cyathophylloid corals, Favosites and Syringopora are the char- 

 acteristic types ; Gyroceras trivolvis is obtained occasionally at 

 the limekilns ; Atrypa reticularis attains large size as it does 

 also in the same limestone further west in this State. Some of 

 the layers contain many trilobites. 



