4l6 CHARLES S. PROSSER 



Higher in the formation are massive darker blue limestones, 

 about 240 feet in thickness according to Schuchert or from 50 

 to 150 feet as given in Rowe's report, some of the layers of 

 which contain numerous specimens of Pe?itamerus ^Sieberella) 

 galeatiis. This zone probably represents the Lower Pentamerus 

 limestone of New York, of which the above fossil is a character- 

 istic species. 



In place of the paleontological name Lower Pentamerus 

 limestone, Messrs. Clarke and Schuchert proposed Coeymans 

 limestone.' 



In the upper fifty feet or more of the limestones are frequent 

 specimens of Spirifer macroplenrus characteristic of the Delthyris 

 shaly limestone of New York, with which this zone is correlated. 

 In New York this division of the Helderberg consists of cal- 

 careous shales and shaly limestones with some beds a foot or 

 more in thickness, but in Maryland it is composed mainly of 

 fairly massive limestone. With the exception of the Lower 

 Pentamerus, all the Helderberg limestones are more massive in 

 Maryland than in New York. In place of the term Catskill or 

 Delthyris shaly limestone Messrs. Clarke and Schuchert pro- 

 posed the geographic name of New Scotland beds.^ 



The Becraft limestone, which caps the Helderberg limestone 

 of New York, is apparently not represented in Allegany county, 

 although some eighty-five feet of it occurs farther east in 

 Washington county, Md. 



The thickness of the foundation varies from 750 to 900 feet, 

 and fossils are common in some of the layers. The limestones 

 are valuable for quicklime, ballast, road-metal, and building 

 purposes. The formation is named from the lower limestones 

 of the Helderberg Mountains in eastern New York, and is the 

 equivalent of No. VI of the Pennsylvania survey, and the upper 

 part of the Lewistown formation of the Piedmont folio. 



Oriskany sandstone. — The easternmost area of Oriskany sand- 

 stone is that of Stratford Ridge, to the northeast of Oldtown ; 

 then follows that of the central part of the county bordering 



■Science, N. S., Vol. X, pp. 876,877. ^ Ibid., pp. 876, 877. 



