Tiii rBxrAOB. 



In Eastern New- York, the coarser eediments of the Hamilton group 

 present proportionally few Brachiopoda ; and in some localities are com- 

 paratively barren of all fossils. The Lamellibranchiata, which are the 

 characteristic fossils of the coarser sediments of this group, gradually 

 diminish in number as the finer materials supervene, and the addition 

 of a larger proportion of calcareous matter is accompanied by the advent 

 of great numbers of Brachiopoda, together with Corals and other fossils 

 which are unknown in the eastern part of the State. So great is this 

 change, that were a collection of fossils from the Hamilton group in the 

 counties of Albany and Schoharie to be compared with a collection from 

 the same group in Genesee and Erie counties, the number of species com- 

 mon to both would be less than has been sometimes indicated as passing 

 from one geological formation to another. 



The same conditions hold true in a more marked degree in the Che- 

 mung group, which, in the counties bordering the Hudson river, is 

 nearly destitute of animal fossils, but contain many plant remains. 

 Farther to the westward, a few lamellibranchiates and brachiopods 

 appear, and their number constantly increases to the central counties of 

 the State, beyond which the Brachiopoda greatly predominate over all 

 the other organisms. Nor is this all ; not only do the Brachiopoda 

 increase in number of species and of individuals, but the species are 

 almost entirely distinct from those in the more eastern localities of the 

 group. We notice, moreover, that in these western localities within the 

 State the prevailing fossils present a " carboniferous aspect," or are of 

 generic and specific forms much resembling the prevailing fossils of the 

 acknowledged Carboniferous rocks of the West. We find also among them 

 a few forms which might readily be mistaken for Carboniferous species ; 

 and in one or two instances, there is scarcely room for specific separa- 

 tion. Here again, in a more emphatic sense, do we find the fauna of the 

 same physical group of strata so entirely unlike at points three hundred 

 miles distant, that there are probably no identical species. At the same 

 time, the entire Chemung fauna of the western counties of New- York 

 presents more analogy with the fauna of the so-called Carboniferous 



