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gives some idea of the commingling of faunas at this horizon. For 

 the present this horizon is referred to the Chazy. Two thousand feet 

 of unfossiliferous rocks intervene between this horizon and the Tren- 

 ton horizon, A"*. The total thickness of the exposed Calciferous is 

 about 1,900 feet; of the Chazy, 2,200 feet; of the Trenton, 900 feet. 

 Unlike the lower horizons, the faunas of A"* are closely related to 

 those of New York. They need no description in this place, the only 

 unusual form found being a Brougniartia, a homalonotoid trilobite, 

 which is quite common in the shaly limestones at the top of the Lower 

 Trenton. The shales of the section are fossiliferous at the base and 

 again at the top. The intervening beds are not fossiliferous. At the 

 base the characteristic Utica form, Triarthrus Beckii, is very common ; 

 its vertical range is 300 feet, and this is taken to be the thickness of 

 the Utica shale. The Lorraine shales contain characteristic fossils 

 similar to those found in similar horizons in New York. Not only is 

 there a marked similarity in the fossils, but in the lithological features 

 of the rocks, indicating very similar conditions in the two fields.. 

 During the earlier stages of the Ordovician there seems to have been 

 free communication between Pennsylvania and the Canadian provinces. 

 In the later Ordovician this seems to disappear, and direct communi- 

 cation is established with central New York. 



The Devonian and Carboniferous of Southivestern New York. By 

 L. C. Glenn. ^ 



The paper is based on work done by the United States Geological 

 Survey, in co-operation with the states of New York and Pennsylvania, 

 in the areal geological mapping of the Olean and Salamanca quad- 

 rangles, together with reconnaissance work southward and westward in 

 Pennsylvania. 



The oldest rocks exposed are the upper 700 feet of the Chemung, 

 consisting of argillaceous and sandy shales, with the Cuba sandstone 

 as a thin lentil near the bottom. The Wolf Creek conglomerate suc- 

 ceeds the Chemung and is regarded as a lentil marking the base of, 

 and belonging to, the Cattaraugus shale formation. It is a fiat pebble 

 conglomerate, quite variable in thickness, but usually thin and incon- 

 spicuous, and thins out and disappears westward on the Salamanca 

 quadrangle. Bright red shales first appear within a few feet above the 

 Wolf Creek and with interbedded greenish shales and soft, fine, greenish- 



' Published by permission of the Director of the U. S. Geological Survey. 



