DESCBIPTIOXS OF THE FORMATIONS. 29 



9-12. DEVONIAN AGE. 



9. LOWER DEVONIAN. 



9 Upper Helderberg or Corniferous, This very widely extended formation 

 consists of four important members, the Cauda-galli, the Schoharie grit, the 

 Onondaga limestone, and the Corniferous limestone, the upper member. But 

 in the recent text-books on geology the whole formation is called the Cornif- 

 erous, which was the name given by Eaton to the whole formation of limestone. 

 It forms the Helderberg range, a high ridge which extends through the State of 

 New York, forming a very rich and productive tract of country. This group of 

 strata, as above limited, and designated the Upper Helderberg by Professor James 

 Hall, is, in his opinion, deserving of recognition as the base of the Devonian, the 

 Hamilton group being the middle, and the Portage, Chernung and Catskhl the 

 Upper Devonian. 



9 a. Cauda-galli. This is a fine-grained calcareous and argillaceous sandstone, 

 usually drab and brownish, and blanching by long weathering. It readily strikes 

 the eye by its contrast with its associated rocks, and by the singular marking of 

 impressions strongly resembling the tail of the common barn-yard fowl, from 

 whence its Lathi name of Cauda-galli or cock's-tail. Its fossils have been found 

 in New York and at Crab Orchard, in Kentucky. In New Jersey, northeast of the 

 Delaware Water Gap, this and the Schoharie are three hundred feet thick. 



9 b. Schoharie Grit. This is very much like the preceding, but altogether 

 different hi its fossils. It is a fine-grained, very calcareous grit, or an arenaceous 

 limestone, naturally brown, but weathering to a gray or drab color, containing a 

 great number of fossils peculiar to this stratum, and is found in the mountain 

 one and one-half miles northwest and northeast of Schoharie, New York, and 

 extends by the Helderberg range to Kingston. The Schoharie Grit is a highly 

 fossiliferous formation, and has a wide geographical extension. Its great number 

 of cephalopods gives it a marked character, but it contains other fossils identical 

 with the limestones above. H. 



The 9 c. Onondaga Limestone in New York rarely exceeds ten to fourteen feet 

 in thickness, but is very persistent, and is readily recognized by its light gray color, 

 crystalline structure, toughness, and its numerous organic remains. This is one of 

 the most valuable building stones in the Helderberg division, and has been largely 

 quarried near Syracuse for the canal. It is an imperishable stone, having great 

 power to resist the action of air, water and frost. It is generally the rock over 

 which the water flows at the water-falls on the Helderberg range, as at Perryville 

 and Chittenango Falls, and is remarkably uniform in its character. It is more 

 extensive than the Corniferous proper, and it is very rich in beautiful and char- 

 acteristic fossils. The limestones used for flagging in Syracuse are Onondaga 

 limestone, brought from the typical localities Onondaga Valley and Split-Rock 

 on Onondaga Hill. "When wet they make a fine display of fossils of this 

 formation. This stone is also used for building everywhere in Central New 

 York. 



