CONTRIBUTIONS TO PALJEONTOLOGY. 211 



formation. It seems to me, therefore, that the comparisons can be 

 more satisfactorily made after we shall have become more fully- 

 acquainted with the Quebec and Potsdam species and their stra- 

 tigraphical relations. If there are any points yet in doubt among 

 these disturbed strata, which can be solved by palseontological 

 facts, these few species from the West may perhaps offer some aid 

 in the solution. 



I learn from Sir William E. Logan that an important part of 

 these ancient strata in Newfoundland, of the age of the Quebec 

 group, are comparatively undisturbed and highly fossiliferous. 

 Whenever the fossils from these undisturbed strata shall have 

 been studied, together with those from the nearly horizontal sand- 

 stones of the Mississippi valley, there will be afforded adequate 

 means of making a comparison with the fauna of the disturbed 

 portions of the intermediate country; and thus doubtless some 

 questions, at present undetermined, will find a solution. 



In comparing the older rocks of New-York and of the East 

 generally, with those of the West, it should not be forgotten that 

 there is a long interval on the line of the northern outcrop of 

 these ancient strata, between the St.Lawrence and the western 

 limit of Michigan on the Menoraonee river, where we can expect 

 little aid from palaeontology. The fossiliferous beds of these an- 

 cient formations in Wisconsin lie to the west of what appears to 

 have been a great promontory at the time of their deposition, 

 stretching southward from the region of Lake Superior far into 

 the ancient sea. The disconnexion caused by this promontory 

 between the East and the West, would of itself prepare us to 

 expect a fauna, differing, in a great degree, from beds of corre- 

 sponding age on the opposite sides. 



It has been shown, by the investigations of the Canadian Survey, 

 that not only the Potsdam sandstone, but all the fossiliferous beds 

 below the Birdseye and Black-river limestones are absent from 

 Kingston on Lake Ontario to Lacloche on Lake Huron. From 

 Lacloche to Lake Superior, there is a sandstone coming in below 

 the Birdseye limestone, which, from its position, may be con- 

 sidered as of the age of the Chazy formation*, and equivalent to 



* The "Chazy formation" of the Canadian Geological Survey, in its eastern locali- 

 ties, includes a sandstone which comes in below the greater part of the limestone, 

 leaving from ten to twenty feet of shale and limestone beneath ( Geology of Canada, 

 1863, p. 123). It is apparently this sandstone of the Chazy formation, having in Canada 

 a thickness of fifty feet, which has become augmented in its western extension, while 

 the calcareous part of the formation has partially or entirely disappeared. 



