EOCKS OF THE ATLANTIC COAST OF CANADA, ETC. 805 



There is, however, no certain evidence that any of these beds reach 

 so high as the horizon of the Potsdam *. 



These rocks of Newfoundland and the Acadian Provinces, con- 

 stituting what I formerly named the " Acadian group '' f , are in 

 their lithological characters and fossil remains precise equivalents of 

 the Longmynd, Menevian, and Lower Lingula-flag groups of England. 



In this connexion an important group of rocks is the Atlantic 

 coast series, or gold series of Nova Scotia, described by me in this 

 Society's Journal as far back as 1850 +, and subsequently in * Acadian 

 Geology ' and supplements thereto §. This great series, extending for 

 more than 200 miles along the Atlantic coast of Nova Scotia, consists 

 of dark- coloured quartzite and slate in massive bands, the former 

 predominating below and the latter above, and the whole attaining 

 to a thickness of perhaps 10,000 feet. In its western extension it 

 appears to rest on rocks of Huronian aspect, and where it is invaded 

 by granitic masses and veins (Devonian in age) it assumes the con- 

 dition of mica-schist and imperfect gneiss, being then similar in 

 mineral character to the rocks elsewhere known as Montalban. It 

 has unfortunately afforded no well-characterized fossils. The mark- 

 ings called Eophy ton II and certain radiating bodies (Astropolithon) ^ 

 found in it are, however, similar to those occurring elsewhere in 

 Lower Cambrian rocks. Murray was disposed to regard this forma- 

 tion as corresponding to his Huronian in Newfoundland ; but it does 

 not agree with this either in mineral character or in fossils, and is 

 perhaps rather to be regarded as a great development of the lowest 

 member of the Cambrian, an exaggerated equivalent of the Harlech 

 Grits and Llanberris Slates. In this case, however, it may be expected 

 that it will yet afford true Cambrian fossils. 



In Western Europe, as Hicks has shown, great movements of 

 depression must have occurred in this period, and we have evidence 

 of a similar character in America. If we roughly divide the Cambrian 

 system into three great series, characterized respectively by the pre- 

 valence of the large Trilobites of the genera Paradoxides, Olenellus^ 

 and Dikelocephcdus, we shall find that the former, the true Lower 

 Cambrian, is unknown over all the great continental jplateau of 

 America **. It is strictly a marginal deposit formed at a time when 

 there was probably a great continent west of the then infant Ap- 

 palachians. But the second, or OleneUus-gvoui>, slenderly represented 

 on the coast, appears in force immediately within the great Lauren- 

 tian axis of Newfoundland ft. It is known in the valley of the St. 

 Lawrence by the great masses of limestone full of fragments of 



* Fletcher, ' Report Geol. Survey of Canada ' ; Matthew, Trans. Roy. See. 

 Can. 1886 ; Canadian Record of Science, 1887- 

 t Acadian Geology, 1868. 



I Quart. Journ. Geol. Soc. vol. \i. § 1868 and 1878. 



II Selwyn, Report Geol. Survey. 



•[[ Acadian G-eology, Supplement, p. 82. 



** Walcott apparently places the lower portion of the Wahsatch section in 

 Utah in the Lower Cambrian ; but this may belong to a western marginal area, 

 ft Murray's ' Newfoundland '; Billings's ' Palteozoic Fossils.' 



