812 SIE J. TP. DAWSOiN" 017 THE EOZOIC AND PALEOZOIC 



plain of the St. Lawrence to which the Montreal and Beloeil Moun- 

 tains belong. 



In proceeding to the west and north the Helderberg Limestones 

 appear in great force at Cape Bon Ami in Northern New Brunswick, 

 where they are rich in fossils and associated with beds of trap. Both 

 limestones are largely developed in Bonaventure and Gaspe, and the 

 lower member in the Island of Anticosti, so that here as in previous 

 periods the area of the Gulf of St. Lawrence corresponds with the 

 interior plateau rather than with the coastal region. In some 

 respects, indeed, this area presents an exaggeration of the interior 

 conditions, since in Anticosti there is apparently a gradual passage 

 from the limestones of the Hudson-river group to those of the 

 Clinton, without the intervention of sandstones similar to the 

 Oneida and Medina of New York and Ontario. In so far as I am 

 aware there is also an absence of beds representing that condition of 

 deserts and salt lagoons represented by the Salina or Onondago salt- 

 group. In this last respect, as in so many others, the conditions of 

 the eastern districts of America conform to those of Europe, and not 

 to those of the interior plateau of America. 



In America as in England the Silurian of the maritime districts is 

 unconformable to the Ordovician, though this does not hold in Anti- 

 costi or in the inland region. 



Lithologically the English Silurian is more perfect than that of the 

 East Coast of America, as containing, in the Wenlock Limestone, a 

 better representative of the Niagara formation. The unequal cha- 

 racter of this limestone, however, and its thinning out toward the 

 south-west, bring the series into harmonj' with that in Nova Scotia. 

 The Ludlow rocks are perfect representatives of the Upper Arisaig 

 series of Nova Scotia, and the fossils are remarkably similar, much 

 more so than in the case of the Arisaig and the inland Helderberg 

 in any locality known to me*. 



In England the trees which I have named Nematodendrece appear 

 first in the Denbighshire Sandstone at the base of the Silurian t. In 

 America they appear in the Helderberg series. Placoganoid fishes 

 have recently been recognized in the Silurian in New Bruns- 

 wick:!:. 



The eurite and tufaceous rocks of the Silurian of the West of 

 Ireland appear to be the principal British representatives of the 

 abundant rocks of volcanic origin associated with the Upper Silurian 

 in Nova Scotia and New Brunswick §. 



In summing up the Eozoic and older Palaeozoic rocks of the Mari- 

 time Provinces I may reproduce here, with some slight additions, the 

 table given in the Supplement to ' Acadian Geology,' 1878. 



* Acadian Geology and Supplements. 



t Hicks, Quart. Journ. Geol. Soc. vols, xxxvii. and xxxviii. ; Dawson, ibid. 



+ Matthew, ' Canadian Eecord of Science,' 1886. 



§ Murchison, ' Siluria.' 



