﻿Problems in Quebec Geology. 491 



Marcou regarded the presence of the Calciferous types 

 of fossils as iUustrations of the " Theory of Colonies" 

 (Barrande's), and held that these forms received their full 

 development at a later period. These peculiar colonies of 

 fossils were supposed to occur in lenticular masses of 

 limestone, enclosed in the slate. Their presence wa& 

 recognized by Marcou both at Levis and Phillipsburgh,. 

 and the associated slates, limestones and conglomerates- 

 were by him considered to be a little higher in the series 

 than the Georgia slates, which were supposed to represent 

 the lowest part of the Taconic. 



The controversy between Logan and Marcou at length 

 drew from Billings a statement, after carefully working 

 out all the facts connected with the fossil contents of the 

 different divisions, to the effect that the fossiliferous 

 Quebec Group was apparently on the same horizon as the 

 Llandeilo of England and Australia, and the equivalent of 

 the Calciferous and Chazy of the American scale of forma- 

 tions ; and he also showed from tlie evidence that their 

 position was in reality at the base of the Lower Silurian, 

 instead of at the summit, where they had so long been 

 placed by some ; and not, on the other hand, beneath the 

 Potsdam, as was maintained by Marcou. He regarded the 

 strata of the group as a peculiar development, the upper 

 limit of which could scarcely be newer than the Black 

 River formation or older than the middle of the Calciferous. 



The views of the structure of this group, as given in the 

 Geology of Canada, 1863, may be briefly summed up as 

 follows : The Quebec Group was divided into two portions 

 stratigraphically, viz., the Levis and the Sillery, of which 

 the latter was regarded as the upper member ; and into 

 two divisions lithologically, viz., a fossiliferous sedimentary 

 and a crystalline metamorphic, the latter of which was 

 held to represent the former in a different condition, the 

 Sutton Mountain rocks being supposed to represent, in 

 part at least, the Sillery formation. 



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