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Devonian, yet most palaeontologists now agree that the 

 age of the Little River group is approximately that of the 

 Millstone Grit. Furthermore it does not appear that the 

 stratigraphical evidence of the Devonian age of the Little 

 River group is any more definitely proven than in the case 

 of the Riversdale-Union series. (4) The argument that 

 the Riversdale-Union series cannot be younger than and 

 therefore overlie the Limestone series because of its absence 

 from such a position in such relatively clearly developed 

 sections as the Joggins and at Sydney, is, in part at least, 

 met by the results of recent work by Hyde in the Sydney 

 basin (see later pages). (5) The main argument as put 

 forward by Fletcher, that the Riversdale-Union is uncon- 

 formably overlain by the Limestone series, remains to be 

 considered. Those who disagree with Fletcher's con- 

 clusions are forced to adopt one or more of the three 

 following explanations. (a) That, Fletcher has placed 

 together under the heading of Devonian, different groups 

 of strata of diverse ages and that where the Limestone ser- 

 ies unmistakably overlies 'Devonian' strata, the older mea- 

 sures are not the equivalent of the Riversdale-Union series. 

 That in some instances such may be the case, is demons- 

 trated in the instance of the Horton series near Windsor 

 and of the lower Devonian of Arisaig both of which groups 

 almost of a certainty unconformably underlie the Carboni- 

 ferous Limestone series but are not the equivalents of 

 the Riversdale-Union series, (b) That, where the Rivers- 

 dale-Union is unmistakably overlain by strata of Carboni- 

 ferous age, Fletcher was mistaken in correlating the over- 

 lying measures with either the Carboniferous Conglomerate 

 or the Carboniferous Limestone. Except possibly in one 

 instance, no independent attempt has yet been made to 

 prove this contention, (c) That, where Riversdale- Union 

 and members of the Mississippian are in contact, Fletcher 

 was mistaken in regard to his interpretation of the struc- 

 tures. In this connection it is justifiable to point out, that 

 though Fletcher was emphatic in his oft repeated declar- 

 ation of the unconformable superposition of the Limestone 

 series upon the Riversdale-Union, yet in no instance did 

 he present detailed statements of the evidence of such a 

 relation but mainly was content to assert that at various 

 points one division unmistakably overlay the other. That 

 mistakes of interpretation may have arisen is not an 

 unwarranted supposition in view of the fact that the geolo- 



