272 C. SCHUCHERT — LOWER HELDERBERG-ORISKANY FORMATIONS 



Thin bedded bluish limestone with zones of sliale. 

 Bryozoa abundant. Near the top occurs a small 



Transition variety of G. galeala and Favosites lielderbergiae, and 



tow aid the bottom Leperditia alta, Goniophora dubia, 

 [ and Spirifer vanuxemi. Thickness about 1(50 feet. 



Base not seen. 



Section at Rose Hill, Baltimore and Ohio Railroad {main line) 



Top not seen. 



A series of heavy to thin bedded, light blue lime- 

 stones resembling water limestones. The series is 

 fossiliferous throughout in narrow zones. Has Ten- 

 taculites gyracanthus, Leperditia fabulites, Beyrichia 



Manlius limestone ■{ notata, other Ostraeods, Rhynchospira near globosa, 



Meristella, a small species very common ; OrtMsne&r 

 perelegans, and poor Bryozoa. Thickness about 

 175 feet. 



Base not seen. 



Salina. 



Iii southwestern Virginia the Helderbergian occurs in Lee, Wise, and 

 Scott counties, and is described by Professor J. J. Stevenson* as follows : 



" The Lower Helderberg. — The rocks of this group are exposed in the Poor valley ; 

 on the western end of AVallens ridge; in the valley between AVallens ridge and 

 Powell mountain, in the North Fork gap; and on the southeastern slope of Powell 

 mountain beyond the gap. The exposures are very fair, and a complete section 

 could be obtained without much difficulty. 



" The estimated thickness is not far from 250 feet. For 70 feet from the bottom 

 the series consists of limestones in beds from three to five feet, separated by shales 

 in somewhat thicker layers. . . . Contains abundance of Leperditia. |~This 

 may be the Onondaga or AVaterlime horizon of the Siluric] Overlying this is a 

 succession of coarse grained calcareous sandstones, shales, and silicious lime- 

 stones. . . . 



" The lower sandstone . . . seems to be made up almost wholly of casts of 

 Orthis oblata. Rhynchonella ventricosa f and undetermined Meristella. 



"The silicious limestone yielded Aspidocrinus scutelliformis, Atrypa reticularis, 

 Strophomena rhomboidalis, Spirifer cyclopierus, Rhynchonella nucleolata, Orthis oblata, 

 etcetera." 



In eastern Tennessee, the Helderbergian is not known, but in the 

 western part of the state these beds are from 20 to 100 feet thick. The 

 fauna here is essentially that of the New Scotland beds of New York. 

 In Missouri, the thickness is given as 175 feet, and in Union county, 

 Illinois, the lower 200 feet of the " Clear Creek limestone " are assigned 

 to the Helderbergian. 



*Proc. Am. Phil. Soc, August, 1880. 



