No. 3.] AMERICAN ASSOCIATION. 159^ 



lower rocks, and it had been traced as t'.ir as Gaspe on the St., 

 Lawrence, and was known in Maine and New Brunswick. The 

 formation could be traced from the -iSrd parallel to the 35th 

 parallel, and this extent, taken in connection with the exposures 

 from the erosion of anticlinals where the rocks are folded, will 

 ' give us more than 2,000 miles of outcrop where the rocks were 

 characterized by fossils, often in great numbers, and where the 

 minsrlinji' with other fossils was unknown. After having thus^ 

 hastily sketched the ground occupied by these groups of strata^ 

 the speaker went on to consider their relations to eacii other^ 

 showing sections at different points from the Schoharie Valley ta 

 Central New York, and by a diagram tracing the lines of out- 

 crop and comparative thickness of the several formations over 

 this area. Then calling attention to the asserted mingling of 

 the fossils of the two groups in Illinois and Tennessee, as claimed 

 by Mr. Worthen, he asserted that from his own experience on 

 the Mississippi River no such mingling of fossils is known, except 

 in the debris of the formation ; that the Niagara formation, 

 greatly thinned out, lies below the beds of the lower Helderberg 

 beds, and the fossils are quite distinct. In Tennessee, Safford 

 has shown that the formations are quite distinct, each character- 

 ized by its own fossils. It \vas true that Safford had said that 

 along the line of junction the fossils were sometimes mingled ; 

 but, in the speaker's mind, the fact did not prove them cotempo- 

 raneous ; for the Lower Helderberg beds with their living shells 

 and other fossils might have been deposited directly upon the 

 dead fauna of the preceding groups,' and thus an apparent ming- 

 ling produced. That these formations were nowhere cotempo- 

 raneous was proved by the great thickness of intervening beds in 

 New York and Canada, where sometimes these intervening rocks 

 were over 1,000 feet thick. He concluded by saying that in 

 reversing the facts and considering the known range and extent 

 of the Niagara and Lower Helderberg groups, their close approxi- 

 mation of actual contact over large areas, and their wdde separa- 

 tion elsewhere, there are no two groups of similar composi- 

 ' tion in the entire palaeozoic series so clearly distinct and so un- 

 ' mistakably traceable in their physical and lithological character, 

 as well as in their contained fossils. 



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