ONONDAGA LIMESTONE 363 



The Corniferous limestone, which is now included with the Onondaga, 

 of which it constitutes the upper cherty beds, is well developed through- 

 out Erie county, forming the summit rock of the cuesta. The average 

 total thickness of the Onondaga limestone (including both the Corniferous 

 and the Crystalline beds) is given by Bishop (page 390) as 108 feet in 

 Erie county. The whole of this, however, is not shown on the edge of 

 the cuesta, erosion having removed a great part of the upper beds. The 

 thickness has been obtained from well borings near the southern edge 

 of the outcrop. 



Stratigraphic Summary 



The Siluric section is complete in Erie county, New York, from the 

 Medina sandstone to the Manlius limestone, which in New York state 

 is the upper member of the Siluric. An important, though not very 

 readily noticed, unconformity exists between the Manlius limestone and 

 the overlying Onondaga limestone of the lower Middle Devonian. This 

 unconformity indicates a period of land surface in western New York, 

 during which the Lower Helderberg and Oriskany beds and the Esopus 

 and Schoharie grits were deposited in the east. Thin deposits of a con- 

 glomerate and shaly sand and limestone occasionally occur in hollows 

 in the eroded surface of the Manlius limestone. These may be con- 

 sidered Oriskany, though their age may be anywhere in the Lower De- 

 vonian. A remarkable fissure in the Siluric rocks and bearing evidence 

 of being formed by violent action is filled with pure quartz sandstone 

 containing angular limestone fragments. This was formed and filled be- 

 fore the deposition of the overlying Onondaga limestone. In Ohio and 

 Michigan the Manlius limestone is a brecciated, often conglomeritic 

 limestone, bearing strong evidence of shallow- water and at times dry 

 land. The fauna of the Manlius limestone in Erie count}^ is a recur- 

 rence of the fauna of the Coralline limestone, the Niagara equivalent of 

 Schoharie county. 



Synopsis of the Organic Remains in the Manlius Limestone of 



Erie County 



nematophyton crassum pen hallow 



1896. Nematophylon crassum Penhallow., Canadian Record of Science, July 1896, 

 pages 151-156, plate II. 



This species was identified by Penhallow from a specimen obtained 

 by Mr F. K. Mixer from the upper part of the " Waterlime group " in 

 Buffalo. The specimen came from the Bullhead or Manlius limestone 



LII— Bur,r,. Gbol. Soc. Am., Vol. II, 1X99 



