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rock and the Maitland limestone from Canada round the head of Lake 

 Eric. Another motive for thus referring the Maitland rock, is found 

 in the affinity which prevails between its fossils and those of the 

 Onondaga, Seneca and Marcellus strata. Of the species examined, 

 it contains in common with those formations, atrypa affinis, also an 

 atrypa common at Schoharie, strophomena lincata, a delthyris, com- 

 mon to the Onondaga limestone and to the shales next above that 

 rock in Pennsylvania (Marcellus shales); also cyathophillum ceratites, 

 and a trilobite of the Onondaga limestone. Though these links indi- 

 cate a somewhat near approximation in date, they are not regarded 

 as proving the rock an equivalent of any of the formations mentioned. 

 None of the organic remains are characteristic of any of the strata 

 lower than the Onondaga limestone. What seems most conclusive 

 however of the high position of the Maitland stratum, is its identity 

 with the limestone of Sandusky, the plane of which is but little under 

 the horizon of the Marcellus shales. 



Rocks of the Detroit River, and of the western end of Lake Erie. 

 The persistence of the pitted rock through Upper Canada being 

 ascertained, the next point was to discover the relations of it and the 

 overlying limestones to the strata widely developed about the head of 

 Lake Erie. Uniting the facts collected of the dip and range of the 

 strata in Upper Canada, with the statements contained in the annual 

 reports of Dr. Houghton, the State Geologist of Michigan, it was in- 

 ferred that a gentle axis of elevation passes in a south-south-west di- 

 rection near the lower end of Lake Huron, forming the northern 

 portion of that broad anticlinal rise of the rocks which divides the 

 upper formations of Ohio from their equivalents in Indiana. It was 

 therefore suspected that the pitted limestone and other strata would 

 depart from their north-western strike, seen in Canada, and range in 

 obedience to this axis towards the south-south-west. Should such be 

 the case, it was hoped to unite by actual tracing the rocks of Michigan 

 and Ohio with those of Canada and New York. Pursuing the forma- 

 tion south-westwardly by the borders of Detroit river, Lake Erie and 

 the Maumee, these anticipations were realized. 



The Fossiliferous Rocks of the Detroit River, both in Canada 

 and Michigan, are readily identified by their composition and organic 

 remains with the limestones which overlie the pitted rock on the 

 Maitland. But the pitted rock itself in Gros Isle, at the mouth of the 

 Detroit river, in a position proving its immediate subjacence to these 

 strata, fortunately places this identity beyond a doubt. It is an are- 

 naceous cream coloured limestone, abounding in the characteristic 



