400 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. 



the Point Levis rocks ; the trilobites long before observed by 

 Bigsby not having been rediscovered. In 1856 the present 

 writer, while engaged in a lithological study of the various 

 rocks of Point Levis, found, in the vicintiy of the graptolitic 

 shales, beds of what were described by him in 1857 (Report 

 Geol. Surv., 1853-1856, page 465) as " fine granular opaque 

 limestones, weathering bluish-gray, and holding in abundance 

 remains of orthoceratites, trilobites, and other fossils, which 

 are replaced by a yellow- weathering dolomite." In these, 

 which are probably what Bigsby had long before described aa 

 fossiliferous conglomerates, the dolomitic matter is so arranged 

 as to suggest a resemblance to certain beds which are really 

 conglomerate in character, and were at the same time described 

 by me as interstratified with the fossiliferous limestones, and 

 as holding pebbles of pure limestone, of dolomite, and occa- 

 sionally of quartz and of argillite ; the whole cemented by a 

 yellow-weathering dolomite, and occasionally by a nearly pure 

 carbonate of lime. (Ibid., 466.) The included fragments of 

 argillite (previously noticed by Bigsby), which are greenish or 

 purplish in color, with lustrous surfaces, are precisely similar 

 to those which form great beds in the crystalline schists of the 

 Green Mountain series of the Appalachian hills, which extend 

 in a northeast and southwest course along the southeastern 

 border of the rocks of the Quebec group. I conceive that 

 these argillite fragments (like those in the Potsdam conglom- 

 erate near Lake Champlain, ante, page 268) are derived from 

 the ancient schists of the Appalachians. 



This rediscovery of fossiliferous limestones at Point Levis 

 led to further exploration of the locality, and in 1857 and the 

 following years a large collection of trilobites, brachiopods, 

 and other organic remains was obtained from these limestones 

 by the geological survey of Canada. 



Mr. Billings, who in 1856 had been appointed paleontolo- 

 gist to the geological survey, at once commenced the study of 

 these fossils from Point Levis, and at length arrived at the 

 important conclusion that the organic remains there found 

 belonged, not to the summit of the second fauna, but were to 



