84 PROCEEDINGS OF XHE GEOLOGICAL SOCIETY. [May 1 894, 



these correlations, and there is one error of some consequence which 

 Dawson, at the time the papers were written, shared with other 

 Transatlantic authors, viz., in placing the Olenellus-i&ima, ahove 

 that associated with Paradoocides. This mistake was corrected by 

 Brogger, who demonstrated that in Scandinavia the Olenellus-zonc 

 was at the base of the Cambrian, being succeeded above by the 

 Paradoxides-zone ; and, according to Dr. Hinde, Mr. Walcott has 

 lately verified this sequence in America. 



It would appear from a perusal of Sir J. W. Dawson's first paper 

 that he was there disposed roughly to divide the Cambrian System 

 into three great series, distinguished respectively by Paradoxides, 

 Olenellus, and Dikelocephalug. The former fauna, he remarked, is 

 unknown over the great continental plateau of America, whilst 

 the second, or Olenellus-gwuj), slenderly represented on the coast, 

 appears in force immediately within the great Laurentian axis 

 of Newfoundland, being likowise known in the valley of the 

 St. Lawrence by the great masses of limestone full of fragments of 

 Olenellus, Solenopleura, Hyolitlies, etc., found in the conglomerates 

 of the Quebec group. Of the upper members of the Cambrian, the 

 Dikelocephalus-grouj), or Potsdam Sandstone, is apparently altogether 

 absent in the Acadian provinces. It seems doubtful if any good 

 equivalent of the Potsdam exists in England or Wales. For a long 

 time this same Potsdam Sandstone was regarded by the geologists of 

 America as constituting the base of the Palaeozoic column, since over 

 great areas of Canada and the United States it lies unconformably 

 and directly on the Laurentian. The marginal areas of the Con- 

 tinent have since afforded a great series parallel to the Cambrian of 

 Wales and Scandinavia. In further illustration of this we find at 

 Matane and Cape Rosier true Tremadocs (regarded as a passage- 

 series between Cambrian and Ordovician) filled with Dictyonema 

 sociale and containing fragments of characteristic trilobites. Farther 

 inland, on the main American plateau, these beds are not found, 

 but are represented by the peculiar ' Calciferous ' formation, a 

 dolomite formed apparently in an inland sea and having a charac- 

 teristic fauna of its own. The Author then observes that in the 

 sandstone and limestone series of Durness a group of fossils was 

 long ago recognized by Salter as being of this interior-American 

 type, which does not exist either in Wales or on the American 

 coast. He concludes that the trilobitic and graptolitic faunas of 

 the coast mainly belonged to cold northern currents ; while the 

 ' Plateau faunas ' — richer in cephalopods, gasteropods, and corals 



