The Position of the Cincinnati Group. 105 



be correct, then the Anticosti rocks become highly interestuig, because 

 they give us in great perfection a fauna hitherto unknown to the pale- 

 ontology of North America. When the great thickness of the rocks 

 between the Hudson Eiver and Clinton Groups is considered, it be- 

 comes evident that a vast period of time must have passed away dur- 

 ing their deposition ; and. yet, as the Oneida conglomerate is unfossili- 

 ferous, and the Medina sandstone has yielded but a few inconspicuous 

 species, we have been almost wholly without the means of ascertain- 

 ing the natural history of the American seas of that epoch. The 

 fossils of the middle portion of the rocks of Anticosti fill this blank 

 exactly, and furnish us with the materials for connecting the Hudson 

 River Group with the Clinton by beds of passage containing some of 

 the characteristic fossils of both formations, associated with many new 

 species which do not occur in either. (Geo. of Can., 1856, p. 249.) 



The Medina sandstone in Western New York, in some localities, is 

 highly fossiliferous, and in some places the fossiliferous part reaches a 

 maximum, says Prof. Hall, of more than one hundred feet. 



The Clinton Group is only estimated, in Ohio and other western 

 localities, at 50 feet or less in thickness. In New York and Canada 

 from 50 to 400 feet, and on the Island of Anticosti at 610 feet ; but 

 in Pennsylvania it reaches the great thickness of 1,620 feet. (Geo. of 

 Penn., vol. i., p. 106), 



Prof. Hall says of this group: "In the western portion of the 

 State (N. Y.) the limit between the Medina sandstone and Clinton 

 Group is well defined, and the materials very distinct ; but, in the cen- 

 tral part of the State, we find the same conditions which operated dur- 

 ing the deposition of the Medina sandstone to have been continued into 

 the Clinton Group. The latter commences by a shaly deposit, which 

 is soon succeeded by alternations of sandstone, in character precisely 

 like the Medina sandstone. The general character of the marine vege- 

 tation of the two periods is similar ; and a peculiar type of plants 

 commences its existence in the Medina sandstone, and terminates in the 

 Clinton Group. When we examine the Clinton Group in the central 

 part of the State, its analogies are chiefly with the Medina sandstone ; 

 and it is there a powerful and important formation, presenting, how- 

 ever, great variation in its successive beds, and characters in every re- 

 spect truly protean. In its western extension, the Clinton Group as- 

 similates in character to the Niagara Group, and in the western dis- 

 trict has nearly lost the character which it presents in Oneida county. 

 At the same time that the group assumes a more calcareous character 

 in its western extension, it loses the fossils which were typical of it, 

 and becomes charged with fossils peculiar to calcareous strata. Thus, 



