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NEW YORK STATE MUSEUM 



Oriskanian 



J Esopns grit Cauda-galli grit 



I Oriskany formation Oriskany sandstone 

 " Port Ewen limestone Upper shaly lime-" 



stone (in part) 

 Upper Pentamerus, o 



Helderbergian 



( Lower Pentamerus or £ 

 Coeymans limestone •< Pentamerus lime- | 



( stone hi 

 Manlius limestone Tentacu lite limestone „ 



Upper Siluric 



The Coeymans or Lower Pentamerus limestone 



This formation has a thickness of about 50 feet in this region. 

 It is mainly a rather coarse semicrystalline limestone composed 

 of fragments of shells, crinoids and corals. At intervals the rock 

 is a nearly typical shell limestone or coquina, with the brachiopod 

 shells composing it largely in a perfect state of preservation. 

 These weather out in relief on the exposed edges of the rock and 

 with care may be collected from these surfaces. Even when per- 

 fect shells are abundant, the main mass of the rock is nevertheless 

 formed of fragments, and this fact renders the rock a very com- 

 pact, hard limestone of very uniform grain, and generally of a 

 dark color, the color being due not so much to impurities as to 

 the manner in which light is reflected from the innumerable 

 cleavage surfaces of Hie small calcite grains. 



No coral reef structure has been observed in this rock in any 

 of its exposures, though heads of corals, specially F a v o s i t e s 

 h e 1 de r be r g i a e arc often quite common, more particularly 

 in the lower part of the formation. These corals often appear to 

 be in the place where they grew, in which case they are repre- 

 sented by perfect head®. Not infrequently however coral frag- 

 ments alone are present or are mingled with the unbroken heads. 

 In such cases even the perfect heads are found overturned, while 

 the fragments lie in all positions. 



