PARALLELISM OF THE QUEBEC GROUP. 29 



bee group with its compound graptolites, overlies all those rocks 

 which represent the Durness limestone. 



The Black River and Trenton limestones, the Utica slate and 

 Hudson River of Canada, represent the upper half of the Lower 

 Silurian of England, but the sub-divisions recognized in the two 

 countries cannot be exactly paralleled. It is almost certain that 

 the Hudson River represents a portion of the Bala or Caradoc. 

 I think that the Trenton limestone might well be paralleled with 

 the base of the same group. The Black River may be nearly 

 parallel with a part of the Bala and the highest strata of the 

 Upper Llandeilo. 



I shall now notice briefly Mr. Marcou's last publication,* in 

 which the following section is given in descending order : 



1. Potsdam Sandstone. ........ . 300 feet. 



2. Quebec Group 2,400 " 



3. Point Levis Group 1,000 " 



4. Gilmour Group 400 u 



5. Chaudiere Group 3,000 " 



No facts either physical or palseontological are given by Mr. 

 Marcou in support of the above classification. It is purely con- 

 jectural. He places the limestones and slates of Point Levis and 

 Phillipsburgh, which have yielded nearly all the fossils of the Que- 

 bec group yet discovered, in what he calls the Point Levis and 

 Gilmour groups, the highest beds of which are according to his 

 section 2400 feet below the base of the Potsdam sandstone. 

 From these rocks we have in the Provincial Geological Museum 

 at Montreal the following genera of organic remains : 



Genera of the Quebec Group. 



Eospongia, Stenopora, Tetradium, Petraia, Rhodocrinus, Glyp- 

 ocrinus, Palceocystites, Dictyonema, Graptolithus,\ Obolus, Obo- 

 lella, Lingula, Acrotreta, Leptcena, Strophomena, Camerella, 

 Rhynchonella, Cyrtodonta, JJohpea, Subulites, Murchisonia, 

 Eunema, Pleurotomaria, Helicotoma, Ophileta, Maclurea, Eccu- 

 liomplialus, Metoptoma, Bellerophon, Orthoceras, Cyrtoceras, Li- 

 tuites, Nautilus, jEglina, Agnostus, AmpMon, Ampyx, Arionelr 



* Letter to Mr. Joachim Barrande, on the Taconic Rocks of Vermont 

 and Canada; by Jules Marcou, Cambridge, Massachusetts, August, 1862. 



t There are several sub-genera of Graptolithus, but as the Decade in 

 which they are to be described is not yet published, I am unable to name 

 them with certainty. 



