126 E. W. ELLS ON THE GEOLOGY OP QUEBEC. 



clearly distinguishable from the Trenton proper at several points, as shown by the large 

 collections of fossils made within the last two years both by Prof. Walcott and myself. 



Second, the placing of the citadel rocks and of the Point Levis graptolitic and con- 

 glomerate beds beneath the Potsdam cannot be maintained, since, as regards the former, 

 the evidence of the fossils, as established by Lapworth, Ami and others, shows the zone 

 of those rocks to be more closely related to the Trenton rocks than to the Potsdam, and to 

 be, for the most part at least, above the Levis formation, and therefore far above the Pots- 

 dam, since it has been clearly shown that the Levis conglomerates in undoubted foreign 

 boulders of the conglomerates carry fossils of the Potsdam age, while the fossils in the 

 jiaste or matrix are not lower than the horizon of the Calciferous. Both these divisions 

 must therefore in their stratigraphical arrangement be placed above the Potsdam. And, 

 third, the rocks of Bic, St. Denis and the Chaudière, while carrying Olenellus Tkompsoni 

 and other primordial fossils, have these only in boulders derived from some distant source, 

 or at least from no rocks noto in the vicinity, and consequently should be placed in the 

 upper part of the Cambrian system. 



The observations of Prof Walcott on certain fossils peculiar to the Cambrian rocks, 

 as given in his elaborate work, "The Cambrian Faunas," published as ' Bulletin No. 30, 

 United States Geological Survey, 1886,' throws some light also upon the age of the lower 

 division of the fossiliferous Quebec group. Thus the peculiar fos.sil Obolella, of which 

 presumably two are known in the upper and middle Sillery, is distinctly stated to be 

 characteristic of the middle and upper Cambrian.' In so far as our observations have 

 extended on the fossils of this group, Obolella has not been observed in any beds above 

 the red shales of the Sillery division, though in the beds of this division and in those 

 underlying the red portion, viz., the black, grey and green shales of Division 2 of the Cape 

 Rouge section, Obolella and graptolites are found at several points. Of the Cambrian age 

 of the lower portion of the Cape Rouge section there can be no doubt, and it is equally 

 clear that the whole section from Division 1 upwards to the Levis formation is a gradually 

 ascending one with no well defined break, at least in so far as the study of a number of 

 sections has shown. Subsequently, in the review of my report of 1888, Prof. Walcott, 

 while agreeing with the conclusions of stratigraphy there stated, supposed that the upper 

 member of the Sillery may form the lowest portion of the Ordovician, representing the 

 lowest Calciferous horizon. The difficulty of drawing any hard and fast line between the 

 rocks of the Cambrian and Cambro-Silurian systems as displayed in the Quebec group 

 was pointed out in the report referred to, and the line as fixed at the time was principally 

 owing to the recognition of the Calciferous horizon of the Levis beds and the well marked 

 break in the fossils between these and the directly underlying red and green slates and 

 sandstones of the Sillery, which break was held to form the most convenient line of 

 separation of the two systems. In Prof Walcott's Bulletin, 1886, however, referred to on 

 page 63, in his classification of the North American Cambrian rocks, he regards the lower 

 portion of the Calciferous formation of New York and Canada as properly belonging to the 

 Upper Cambrian, the Potsdam forming the lower portion of that division, so that in this 

 evidence, also, the conclusions already stated in this paper, as regards the division and 

 relative age of the Quebec group rocks, are, it is held, clearly svistained. 



' "Cambrian Faunas," 18S(!, p. 02. 



