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pala;ontology of new-york. 



CORALS OF THE CLINTON GROUP. 



The corals peculiar to this period are comparatively few in number, though in some localities 

 the individuals are extremely numerous. The general character of these corals is similar to those 

 of the Niagara group ; and several species pass from one group into the other, or, in other 

 words, are common to the two groups. I have endeavored to give here only those species which 

 are limited to the Clinton group ; or if one or two species, common to the two groups, are no- 

 ticed, it is because they present some peculiarity not observed in specimens from the Niagara 

 group. 



The condition of the sediment in this group has not been favorable to the preservation of these 

 fossils in the best condition for examination. In nearly all localities the calcareous rocks are 

 more or less silicified ; and though this kind of material preserves the mass, it often obliterates 

 the finer characters. In the green shales the material is too soft to preserve well the fossil corals, 

 and therefore we have not the means of defining them so perfectly as in some of the other 

 formations. 



From the great number of individuals which are crowded into some beds of this formation, 

 extending from Wayne county westward as far as the head of Lake Ontario, we may infer that 

 the condition was favorable for their growth, and that there was no great variation in the depth 

 of the water over this area. This evidence from the corals, contrasted with their almost entire 

 absence in the eastern portions of the group, together vdth the coarse and uneven nature of the 

 sediment in the same parts of the series, shows conclusively that the eastern part of the group . 

 was deposited in situations subjected to great agitation, and probably near to land, or in the 

 direction of conflicting currents. Taking this view of the deposition, it is easy to see how the 

 shaly and calcareous strata of the western portion, quietly deposited in an ocean of moderate . ^ 

 depth, assimilate both in organic and physical characters with the succeeding Niagara group, alsoBT 

 deposited throughout in quiet water ; while in the eastern portions, the contrast is so extreme 

 that they bear little similarity. 



Nearly all the preceding species of plants, the trails and tracks upon the surface, are confined 

 to the eastern portion of the group ; while the fossils yet to be described, belonging to the 

 same, are mostly from its western part, or from points west of Oneida coxmty. The fact should 

 also be remembered, that the eastern character of the group is maintained, to a great degree, in 

 its southern extension beyond the limits of New-York ; while to the west and southwest, it 

 constantly approximates in character to the succeeding group. 



Among the corals which continue their existence into the Niagara group, the Catenipora is 

 the most conspicuous and interesting. It first appears associated with the ore beds in Wayne 

 county, and has been found in other localities. This coral becomes abundant in the Niagara 

 limestone, and its existence has not been traced beyond that period. 



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