108 



PALJEONTOLOGY OF NEW-JOBJC. 



a group so uniform and well characterised as that of Niagara. As I have already shown, the 

 almost total absence of calcareous matter has precluded the existence of nearly all those forms 

 of fossils peculiar to the Niagara group ; and the shales, sandstones, and conglomeritic layers, 

 are marked by the presence of an infinite number and variety of marine plants, with few 

 molluscs, and here and there a fragment of a trilobite of the same species as those in the 

 Niagara group. Even here we perceive, notwithstanding the discordant nature of the materials 

 of the two groups, that they belong to a period during which the same fauna to some extent 

 existed. Although the Homalonotus, Phacops and Bumastis occur in the shaly sandstones of 

 the lower part of the group in Oneida county, they could not exist in any considerable num- 

 bers, or degree of development, on account of the nature and the conditions of the sediment. 



In addition to the influences of the prevailing siliceous and argillaceous character of the 

 strata of this group in the eastern and central portions of this State, we have that of the ores 

 of iron, which, in all situations, appear to be prejudicial to most forms of animal life ; and 

 though these ore beds are apparently made up of organic exuviee, yet fossils are comparatively 

 rare in their immediate neighborhood, or where the hydrate of iron enters into the composi- 

 tion of the surrounding strata. 



I have presented all these facts, that they may be considered in reference to the period from 

 which the fossils are described. Notwithstanding the dissimilar character of the groups in some 

 places, yet regarding their entire extent and character, I am inclined to unite them as one 

 group ; but since they have heretofore been separated and thus published in the Geological 

 Reports, I have preferred to leave the determination of the question to a future time, giving 

 the fossils of each group by themselves, indicating those which are common to both. In order, 

 however, not too widely to separate some of the families, I have carried forward the Crinoidea 

 and Trilobites to be described with those of the Niagara group ; and I should have done the 

 same with the Corals, had they not been already included in the numbering of the preceding 

 plates. 



Regarding the very great advantages to be derived from a minute subdivision among the 

 groups, I am unwilling to describe in conjunction, or as from the same group, fossils that are 

 in a great degree restricted to individual rocks or beds of such group, where it is composed 

 of several members. It is far more easy for the student to unite these, than it would be to 

 separate them ; and to those %vho look at their entire character for the purpose of generalizing 

 these subdivisions, it can offer no objection that they are presented in the order of their oc- 

 currence, the true order of their appearance or coming into existence upon our planet. This 

 must be my only apology with those who think that the science is retarded by numerous sub- 

 divisions, but which appear to me, on the other hand, to facilitate progress, by giving us 

 more exact knowledge for the basis of our generalizations. 



