INTRODUCTION. 
39 
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 Galt, and which Mr. Halt, 
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, 
fipon 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 Megalomus canadensis was found in all these locali¬ 
ties, but most numerous at Galt 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 Loxonema boydii and Euomphalus sulcatus, 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. There 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 
interstratified 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 James Hall, in Foster and Whitney’s Report. 
