HELDERBERG DIVISION. 
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2. Onondaga Limestone. 
Fig. 17. 
This rock, the upper member but one of the Helderberg division, is remarkably uniform 
in character, and is more extensive even than the preceding, or Corniferous limestone. It is 
generally a coarse-grained subcrystalline grey limestone, and contains great numbers of the 
Cyathophyllura, some of which are very large. The Favosites is also very common, and I have 
seen more beautiful specimens of this fossil on the Helderberg mountains in Sharon, Bern 
and Bethlehem, than from any other part of the world. Hornstone occurs in nodules and 
interrupted layers in some localities of this rock. The fossils are numerous, and will be 
described in the Paleontological Report. The following have already been described by Mr. 
Conrad, viz :* 
Dekhyris raricosta. 
Strophomena gibbosa. 
— perplana. 
Atrypa nasuta. 
— unisulcata. 
— acutiplicata, 
Avicula pecteniformis. 
Cypricardites inflata. 
Bellerophon curvilineatus. 
Pleurotomaria poulsoni. 
— unisulcata. 
Asaphus aspectans. 
♦ Vide Prof. Vanuxem’s Report, p. 138, and remarks on synonims. 
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