410 G. L. COLLIE — OEDOVICIAN SECTION NEAK BELLEEONTE 



D'Invilliers* gives a detailed cross-section of Nittany valley and a 

 careful description of the geological structures to be found there. 



In somewhat less detail Lesley j gives cross-sections and descriptions 

 of the rocks in Nittany valley, with especial reference to the iron-bearing 

 limestone. 



Lesley differs from Rogers somewhat in his interpretation of the age 

 of the Magnesian limestone series. He does not consider it to be wholly 

 Calciferous, but assigns the upper portion, with a thickness of 1,000 or 

 1,200 feet, to the Chazy.J He states that the Calciferous II a is almost 

 non-fossiliferous, the Chazy II b is slightly fossiliferous, and the Trenton 

 II c is abundantly fossiliferous. § 



Ewing II gives added descriptions of the rocks, and also a list of the 

 fossils known to him. According to his statement, few fossils are found 

 in the lower part of number II, and those found are mainly fragmentary 

 and indistinct. 



In the catalog of the Survey museum, volume 0.3, Mr C. E. Hall has 

 amplified the list of fossils given by Ewing. 



In this paper the author adopts the term Beekmantown T[ in place of 

 Calciferous or Magnesian limestone; the term is much more suitable 

 than the old names and ought to replace them. 



The writer has found the Beekmantown to be fossiliferous, and has 

 discovered three distinct fossiliferous horizons in the formation. There 

 is apparently no true Chazy present, but rocks containing the fauna of 

 the Stones River group,** which includes the Birdseye zone of New York 

 as its upper member, follow immediately on the Beekmantown. These 

 in turn are followed by the Black River and Trenton groups, above 

 which follow in order the Utica and Lorraine shales. 



The chief lithologic features of the rocks are set forth in the following 

 table, together with the thickness of each subdivision : 



GROUP I.-BEEKMANTOWN STAGE 



1. Dark, compact, thick bedded limestone, frequently oolitic in structure, 



containing lenses of white silicious sandstone 150 



2. Variegated, dark and light gray limestone, breaking with conchoidal 



fracture 35 



* Pennsylvania Second Geol. Survey, vol. T. 4, p. 28. 



t Pennsylvania Geol. Survey, 1892, Summary Final Report, vol. i, p. 365. 



J Pennsylvania Geol. Survey, 1892, Summary Final Report, vol. i, p. 517. 



§ Pennsylvania Geol. Survey, 1892, Summary Final Report, vol. i, p. 501. 



II Pennsylvania Second Geol. Survey, vol. T. 4, p. 427. 



^ Clark and Schuchert, Science, vol. 10, pp. 874-878. 



**The Stones River group was originally proposed by Safford in 1851 (Am. Jour. Sci., 2d series, 

 vol. xii, p. 352), and in 1897 was resurrected and redefined by Winchell and Ulrich in Introduction 

 to Minn. Geol. Survey, vol. 3, part II, p. xc. 



