No. 4.] HUNT — ON CAMBRIAN AND SILURIAN. 427 



sequence from the Trenton limestone and the Utica slate, of 

 clay-slates and limestones, with graptolites and other fossils, 

 followed by conglomerate-beds supposed to contain Trenton 

 fossils, red and green shales and green sandstones; the details 

 of the section being derived from the neighborhood of Que- 

 bec and Point Levis, and from the rocks first described by 

 Bigsby. As farther evidence with regard to the supposed 

 horizon of these rocks, to which he subsequently (in I860,) 

 gave the name of the Quebec group, we may cite a letter 

 of Sir William Logan, dated November, 1861, [Amer. Jour. 

 Sci. II, xxxiii, 106,] in which he says " In 1848 and 1849, 

 founding myself upon the apparent superposition in Eastern 

 Canada of what we now call the Quebec group, I enunciated 

 the opinion that the whole series belonged to the Hudson-River 

 group and its immediately succeeding formation ; a Leptmna 

 very like L. sericea, and an Or this, very like 0. testudinaria, 

 and taken by me to be these species, being then the only fossils 

 found in the Canadian rocks in question. This view supported 

 Prof. Hall in placing, as he had already done, the Olenus rocks 

 of New York in the Hudson-River group, in accordance with 

 Hisinger's list of Swedish rocks as given in the Lethcea Suecica 

 in 1837, and not as he had previously given it." 



The concurrent evidence deduced from stratigraphy, from 

 geographical distribution, from lithological and from paleontologi- 

 cal characters, thus led Logan, from the first, to adopt the views 

 already expressed by Bigsby, Emmons and Bayfield, and to 

 assign the whole of the paleozoic rocks of the south-east shore of 

 the St. Lawrence, below Montreal, to a position in the New York 

 system above the Trenton limestone. While thus, as he says, 

 founding his opinion on the stratigraphical evidence obtained in 

 Eastern Canada, Logan was also influenced by the consideration 

 that the rocks in question were continuous with those in western 

 Vermont. Part of the rocks of this region had, as we have seen, 

 originally been placed by Emmons at this horizon, while the 

 otliers, referred by him to his Taconic system, were maintained 

 by Henry D. Rogers to belong to the Hudson-River group ; a 

 view which was adopted by Mather and by Hall, and strongly 

 defended by Adams, at that time engaged in a Geological Survey 

 of Vermont, with which in 1846 and 1847, the present writer 

 was connected. 



As regards the subsequent paleontological discoveries in these 



