270 C. SCHUCHERT — LOWER HELDERBERG-ORISKANY FORMATIONS 



merus [Gypidula] galeatus."* In Otsego county this limestone has a 

 thickness of not less than 80 feet. 



The Coeytnans limestone " graduates above into a shaly formation, 

 which was designated in the New York Reports as the Delthyris shaly 

 Limestone, from the abundance of this genus of fossils [Delthyris === 

 Spirifer]."f The " Delthyris shaly limestone" or New Scotland beds is 

 the most ])rolific in fossils, not less than 298 species having been found 

 in New York alone. 



The upper member of the Helderbergian is generally known in New 

 York as the Upper Pentamerus limestone. Vanuxem named it the 

 " Scutella limestone," because of the presence of certain large crinoidal 

 plates, while Gebhard called it the "Sparry limestone," owing to its 

 strong crystalline nature. Darton, with Hall's consent, has recently re- 

 named it " Becraft limestone," a name here adopted. 



All these rocks are well exposed in the Helderberg hills of New York, 

 particularly in Albany and Schoharie counties, where they have a thick- 

 ness of from o00 to 400 feet, but thin out rapidly toward the west. There 

 is " scarcely any evidence of their existence in New York west of Oneida 

 county."" J 



Following the Helderberg hills in a southwesterly direction " through 

 Pennsylvania, Maryland, Virginia, and Tennessee, we everywhere find 

 the same group of strata, and bearing everywhere more or less the same 

 species of fossils. ... In some localities in the middle and southern 

 [southwestern] parts of Tennessee, the collections of fossils are so like 

 those from the Helderberg mountains, near Albany, that but for their 

 color and here and there a difference in the development of certain 

 forms, there would be little to distinguish the two localities." § The 

 same is also true of the Helderbergian of Indian Territory. 



In Monroe county, in eastern Pennsylvania, the Helderbergian has a 

 thickness of about 600 feet, but thins westward, and in Perry county is 

 only 350 feet thick. In Pennsylvania these beds are known as division 

 number 6, and locally as the "Stormville shales." The latter "grow 

 bud' and sandy when traced westward from the center of Monroe county, 

 and, as seems most probable, become continually coarser, until they are 

 consolidated with the Oriskany sandstone." || 



In western Maryland, the Helderbergian series is represented in the 

 " Upper limestone series " of the Lewiston formation, and appears to be 

 more extensively developed stratigraphically than in any other region 



* Hull, ',s:,\). 



t Hall, is.")!), p. 33. 



J; Hall, L859, p. 37. 



I Hall, 1859, pp. 37-38. 



|| I. C. White, Geol. Survey of Pa., vol. C C, 1882, p. 132. 



