HELDERBERG DIVISION. 
337 
1. Odontocephalus selenurus. 
2. Cyrtoceras undulatus. 
3. Strophomena undulata. 
4. Orthis lenticularis. 
5. Atrypa prisca. 
6. Strophomena lineata. 
This rock is the uppermost member of the Helderberg division. The, above name was 
given to a limestone containing hornstone, by the late Prof. Amos Eaton, and is retained as 
appropriate to this limestone, though hornstone and chert are not peculiar to this rock. These 
minerals are also found to be common in the other calcareous members of the Helderberg 
division. The Corniferous limestone is characterized by its fossils, which are numerous. The 
coiled shells called the Cyrtoceras, of which there are several species, are perhaps those that 
may be considered as characterizing this limestone. The woodcut above, prepared by Prof. 
Vanuxem to illustrate some of the characteristic fossils of the Third district, will answer 
equally well for the First district. The strata are the same, slightly varied in mineralogical 
composition, and contain the same fossil remains. The Corniferous limestone is used in Scho¬ 
harie for burning lime, and is considered as making the whitest and strongest lime. Speci¬ 
mens of the Cyrtoceras are very frequently found in breaking the stone at the limekilns. 
The rock is coarsely subcrystalline grey limestone, containing courses of nodules of horn¬ 
stone. In some places the rock is darker colored and more impure. 
The Corniferous limestone is found from near Leesville, in the west part of Schoharie 
county, ranging eastward by Cobleskill and Schoharie, to the top of the Helderberg, thence 
southeast and south to Esopus falls ; and patches of it are seen occasionally among the up- 
heaved masses about Kingston, Hurley, Bridgeport, Rochester, &c. The fossils will be 
Geol. 1st Dist. 43 
