INTRODUCTION. 3| 



the belief that there exists a continuous group of strata, marking a 

 stage in the Palaeozoic period above the Niagara group, and perhaps in 

 some places not sharply separated from it, but which will exhibit a 

 distinctive fauna. The determination of this question must be made by 

 examinations through Canada West and the Western States, since the 

 formation would appear to lie conformably over the Niagara group, 

 and to follow the same trend to the westward. The strata holding this 

 position in Canada have been shown by Alexander Murray, Esq., of 

 the Canadian Survey, in a letter to Sir William Logan, to hold a 

 defined position above the Niagara group*. 



The Onondaga-salt group, with its gypsum beds, has heretofore been 

 described as it occurs in the State of New- York. It is likewise known 

 to extend through the peninsula of Canada West, and forms a part of 

 the island of Mackinac ; while the pebbles of porous limestone forming 

 the beaches on all the islands of this region, show how extensive has 

 been the destruction of this group of strata. Westward from Mackinac 

 these rocks have not been recognized as far as the peninsula, nor in the 

 peninsula of Green Bay ; and I have shown how, from their destruction, 

 have resulted portions of Lake Huron and Lake Michiganf . It is only 

 near Milwaukie that some beds have been discovered, by Mr. Lapham, 



•"With regard to the age of the group of rocks which appear at Gait, and which Mr. Hall 

 proposes to class as a part of the Gypsiferous instead of the Niagara formation, this season's 

 examination has tended to show that his suggestion is founded upon correct data. 



" The rocks in question are extensively displayed on the Grand river, from Middleton bridge on 

 No. 21, Cth Concession of Dumfries, all the way to the forks of the Speed above Preston; at Guelph, 

 upon the Speed; between Elora and Fergus on the Grand river; and on the banks of the Rocky 

 Sauquin. The fossil Mr. Hall proposes to call Megalomxu canadensis was found in all these locali- 

 ties, but most numerous at Gait and at Elora, and in all cases only among the upper beds of a group 

 of limestone strata of peculiar character. Numerous spiral shells, among which we supposed we 

 could recognize the Jxixonema boydii and Euomphahis sulcaiua, and numerous corals, were found 

 associated with the M. canadensis, and also in most of the lower beds of the group, especially at 

 Elora, where there is a vertical section of the group exhibiting about 80 feet. Ttere is an undoubted 

 difference in mineral as well as fossil character, between these limestones and others on which they 

 repose. The inferior rock is a dark brown and sometimes almost black, very bituminous limestone 

 interstratiflcd with black bituminous shales; whereas the upper one is of a pale yellowish or drab 

 color, sometimes granular in structure and apparently entirely free from bituminous matter. The 

 transition from the lower to the higher rock is well developed at Guelph on the river Speed." 



t Jamks Hall, in Foster and Whitney's Report. 



