164 SUBDIVISIONS OF THE CARBONIFEROUS SYSTEM 



No difficulty has been experienced in separating the various 

 geological formations in the Counties of Nova Scotia mentioned 

 above, nor of understanding their taxonomic relations. The most 

 excellent work of Mr. Hugh Fletcher, of the Geological Survey 

 of Canada, who kindly furnished me with maps and plans of the 

 region in question, shows clearly the true and natural order of 

 sequence of the formations. The main question at issue, how- 

 ever, has been where to place the series of sediments hitherto 

 known, and designated by Mr. Hugh Fletcher as the "Rocks of 

 Union and Riversdale " : in the Carboniferous or in the Devonian 

 system. Mr. Fletcher would place them in the Devonian. I 

 include them as formations in the Carboniferous system (and 

 would also classify in the same system the red rocks of Mispec 

 and the Lancaster fern-ledges of New Brunswick, which hold 

 much the same flora and fauna). The various formations of the 

 Carboniferous system do not form an unbroken succession of 

 sedimentary strata in the disputed region either of Pictou, Col- 

 chester and adjacent counties. Great breaks and unconformities 

 appear on every hand. 



It may not be considered out of place here to look for a 

 moment at some of the principles involved in such questions as 

 arise in this problem. Portions of formations constituting cycles 

 of sedimentation or of constructive forms, marking peculiar 

 physical conditions of deposition, followed by periods of erosion, 

 and subsequent depositions, occur at various horizons, and were 

 it not for their entombed faunas it would be most difficult to 

 state in which of the subdivisions of the Palaeozoic column to 

 place them. Where sedimentation as marked by cycles of con- 

 structive forms is not continuous, the basis or principle upon 

 which the separation of the different members of the series 

 depends, must obtain in the palseontological evidence collected 

 in the various members whose succession, though not perfect, 

 is, nevertheless, known as to its order. 



Similarity in the types or organic forms found, assists one in 

 uniting series of sediments as part and parcel of one system, just 

 as dissimilarity enables one to separate series of sediments from 



