PORTAGE GROUP, 
249 
and we shall do well to bear in mind, what has been before remarked, that the conditions of 
the ocean bed and the nature of the sedimentary deposits has greatly influenced the character 
of the organic forms. It may thus happen that the fossils so typical of the Chemung group 
commenced their existence in the eastern part of New-York much earlier than in the western 
part; and, therefore, the strata equivalent in age to the Portage group may there contain 
fossils which at the west appear only at a later period. 
[Geol. 4th Dist.] 
32 
