392 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



that, perhaps, partly from its thickness and remarkable extent. In 

 this, it contrasts strongly with the limited fossil-connexion maintained 

 in the old continent by localities not very far removed from each other, 

 as Bohemia and Sweden. 



Fossils recurrent in New York. — This group receives from those 

 preceding it twenty-one fossils, principally, as before said, from the 

 Hamilton group, and in the east of New York mostly. 



The Chemung is Devonian, says Daniel Sharpe (Geol. Journ. iv. 

 p. 155) ; and but for its separation from the Hamilton group by the 

 almost unfossiliferous Portage group, the two ought not to be kept 

 separate. Only two Molluscs are derived from the Portage group ; 

 and one, Leptcena crenistria, from the Clinton of the Silurian system. 

 It has four organic remains in common with Oriskany Sandstone, only 

 one with Caudagalli Grit, namely the singular fucoid giving name to 

 that stratum. It has no relations whatever with Schoharie Grit, Onon- 

 daga Limestone, and Marcellus Shale ; and with Genesee Slate but 

 one common fossil, Atrypa reticularis. The Chemung group receives 

 four species from the Corniferous Limestone, and two from Tully 

 Limestone. We see from all this, that fossil-connexions are not 

 exclusively influenced by the mineral character of the rock. 



Fossils typical. — The large number of sixty are peculiar to this 

 group, principally Brachiopoda and Monomyaria, which are inha- 

 bitants of mixed sediments. The other ten orders are almost alto- 

 gether absent, as far as we know at present. To find in any 

 shale or sandstone a Cephalopod, an Echinoderm, or an Annelid, 

 would go far to prove that that shale, &c. did not belong to the 

 Chemung period. 



Catskill Group. 



Mineral Character. — It consists of light-coloured greenish-grey, 

 or fine-grained red sandstone, interspersed with layers of red or dark- 

 coloured shale and slate, with beds also of grindstone-grit. There 

 is, further, a mass apparently composed of fragments of hard slate 

 cemented by limestone (the "cornstone" of England) ; but it is only 

 a few feet thick. 



We have also conglomerates, more or less coarse, of a greyish, 

 greenish, or red colour. 



All these are arranged as follows, from above downwards : — 



1 . Conglomerates and coarse schists. 



2. Red shales, slates, and grits. 



3. Grey and greenish-grey slaty grits. 



4. Chocolate-coloured grits, with red shales and slates (Mather, 

 Rep. p. 302). 



The stratum of brecciated and conglomeratic limestone, marked 1 29 

 by Mather, in his detail of layers, as they occur in the Catskill 

 Mountains, and found not far from the base of this group, is met 

 with over a large area, though rarely more than 2 feet thick. It is 

 therefore a good reference-stratum. It often contains carbonates of 

 copper, iron, and zinc, but in very small quantities (Mather, 

 Report, p. 307). 



