PARALLELISM OF THE QUEBEC GROUP. 23 



River forms ; but fortunately several of them are silicified ; and 

 when perfect specimens are worked out of the limestone-matrix, 

 by the application of acid, they are found to differ, not a great 

 deal, it is true, but, to such an extent that many naturalists would 

 pronounce them to be distinct from those of the two formations 

 mentioned. All the genera of trilobites that have been found in 

 the Trenton, except Acidaspis, JBronteus, Calymene, and Encrinu- 

 rus, occur in the Quebec group. On the other hand we find all 

 the Potsdam and Taconic genera, except Atops, Bathynotus, and 

 Aglaspis. Along with these there are several new genera of tri- 

 lobites and some European types, such as Ampyx, Nileus, Hoh- 

 metopus and JEglina, not yet known as occurring in the north- 

 western portion of the- palaeozoic basin of America. 



We have thus in the Quebec group, that intermingling of the 

 types, of the first and second faunae, that must be expected in a 

 formation whose true position is low down in the Silurian 

 series and near the primordial zone. And as the species properly 

 belonging to the second fauna, are vastly in the majority, we have 

 assigned to the formation a position a little above the Potsdam 

 group. 



Such being, in substance, the general conclusion that has been 

 arrived at, i. e. that the Quebec group is situated in the lower half 

 of the lower Silurian, it is next to be shewn, to which of the Ame- 

 rican sub-groups it can be paralleled. And here we must, per- 

 haps, make some allowance for the existence of zoological pro- 

 vinces in the Silurian seas, similar to those of the present day. 

 If a line be drawn following the St. Lawrence from its mouth to 

 the neighbourhood of Quebec, thence to the northern extremity 

 of Lake Cham plain and then along the lake to Whitehall; thence 

 to Albany and along the Appalachians to Tennessee, I think it 

 will be found, that the palaeozoic rocks lying south-east of that 

 line contain some groups of fossils, to a great extent specifically 

 distinct from those imbedded in rocks of the same age lying north- 

 west of it. In this way we may in part, but not altogether, 

 account for the extraordinary fact of the Quebec group yielding 

 such a large number of species distinct from those occurring in 

 New York and Canada west. 



Or, it might be explained, by supposing that in the south-eastern 

 region, there are deposits which do not exist in the north-west. 

 The thickness of the Calciferous and Chazy in Canada west of the 

 line, cannot be much over 600 feet, while the Quebec group is at 



