291 



we find, in ti-acing these rocks westward from New York, a tendency 

 of the fauna to assume a decided carboniferous character. In fact, in 

 some parts of north-western Ohio, this character is as decided as that 

 of the fauna of the Burlington Limestone, and considerably more 

 so than that of the lower beds at Burlington. 



On the other hand, a direct continuity of the strata of the Chemung 

 rocks of New York can be traced from that State to those of Ohio 

 before mentioned, and Prof Hall seems very naturally to have inferred 

 that, but for the interposition of the Cincinnati axis, their continuity 

 might have been traced to those rocks of the West which he has re- 

 ferred to that group. This opinion appears to have been fully justified 

 by the relative position of the rocks above and below them in the 

 Western localities. 



Messrs. Meek and Worthen seem to have made the presumed want 

 of specific identity of species thus far discovered in the rocks of the 

 western localities, with those now known in the Chemung rocks of 

 New York, the principal reason xbr separating them from those rocks ; 

 and their affinity with the carboniferous limestones of the West, for 

 supposing them to be properly referable to the Carboniferous system, 

 " or at any rate much more recent than the Chemung." 



If, as we believe, and have attempted to show, the Chemung rocks 

 of Ohio are a direct continuation of the Chemung of New York, we 

 cannot think it possible that those Ohio rocks, containing, as they do, 

 a fauna so decidedly carboniferous, can belong below those rocks which 

 underlie the Burlington limestone in the West, and which, if at all 

 referable to the Carboniferous system, must occupy its very base. We 

 do not lose sight of the fact that some of the species of the Hamilton 

 group pass up into and intermingle with those of the Chemung rocks 

 of eastern New York, and that this group there presents decided Devo- 

 nian characters ; nor that in the West the rocks which we deem their 

 geological equivalents are closely alHed to the carboniferous lime- 

 stones. We admit also that this great difference in the character of 

 the fauna is not fully explained ; but it will be borne in mind that a 

 similar state of things exists in Europe, where the rocks have been 

 carefully studied for years, while all the ground has hardly been 

 carefully reconnoitred in our own countiy. 



The most northerly point in the Mississippi valley at which we have 

 observed these rocks, is near Indiantown, in Tama county, Iowa, but 

 this locality has not been thoroughly explored. At Burlington the 

 rocks have been minutely described by one of the writers in a previous 

 paper,* and also in the appendix to the 1st Vol. of Geology of Iowa. 

 At various points in Missouri and Illinois we have sections and de- 



* See Art. 2d, Vol. vii., Boston Journal of Natural History. 



