124 TWENTY-SEVENTH REPORT ON THE STATE MUSEUM. 



relations of the coralline limestone, all of which have tended 

 to confirm the views there expressed. This coralline limestone 

 in its attenuated form may be recognized in the valley of the 

 Hudson river underlying the water-lime formation at numerous 

 localities. 



Now returning along this line of outcrop to the Niagara 

 river, and following the formation to the north-west, we find it 

 expanding in thickness and area through Canada West to 

 Cabot' s Head ; appearing in the islands along the eastern 

 and northern side of Lake Huron, and stretching across the 

 peninsula from St. Joseph's river to the outlet of Green Bay ; 

 thence occupying the principal part of the peninsula between 

 Green Bay and Lake Michigan, it expands to the southward 

 beyond the southern limits of that lake, and thence trends to 

 the west and north-west through Illinois and Iowa. From the 

 Niagara river westward, the formation is chiefly a magnesian 

 limestone, and in many localities carries an abundance of fos- 

 sils ; both the physical and palseontological evidence leave no 

 doubt as to the age and relations of the formation. 



Returning again to the eastward and southward, we find 

 that the anticlinal movement, which elevated the islands in the 

 western part of Lake Erie, has brought up the Niagara forma- 

 tion in the adjacent parts of Ohio, where it is marked by the 

 presence of a greater or less proportion of its characteristic 

 fossils. Here it stretches in a low axis for miles to the south 

 of the lake, and thence spreads and outcrops on either side of 

 the rocks of the Hudson river and Trenton age, which form 

 the central or lower visible portion of the Cincinnati axis. 



Following this direction it extends through Kentucky and 

 Tennessee, everywhere carrying its characteristic fossils. 



Throughout all this extent, until the formation reaches 

 Tennessee, there is no question raised as to the identity and 

 purity of the Niagara group. Here, it is said that the fossils 

 of the Niagara are mingled with those of the Lower Helder- 

 berg group. And again, on the Mississippi river, in Illinois 

 and Missouri, we are told that this mingling of the fossils of 

 the two periods occurs. 



But before proceeding to discuss this part of the question, 

 let us for a moment give attention to what is termed the Lower 

 Helderberg group in its typical localities. 



