31 



of Phyllograptus and other graptolites, indicate a close 

 similarity to the fauna of the Levis. The Sillery also 

 contains layers of limestone conglomerate, but the pebbles 

 differ from the conglomerates in the Levis in containing 

 Lower Cambrian fossils almost exclusively, although an 

 occasional specimen has been found which indicates the 

 Dikelocephalns fauna. The thickness of the Sillery 

 is unknown. 



HISTORICAL NOTE. 



The earliest account of the rocks in the vicinity of 

 Quebec and Point Levis is in a paper published in 1827 

 by Dr. J. Bigsby [1]. Bigsby divided the rocks into 

 three series, the gneiss, shell-bearing limestone, and a 

 slaty series with conglomerate, and decided that the 

 sedimentaries belonged to the Carboniferous series. Logan 

 [2] in 1843, thought that the strata of Levis were below 

 the limestone north of the St. Lawrence, but finally adopted 

 the view that they were above, and thus the equivalents 

 of the Hudson river and Lorraine of New York State. 

 In 1855, Logan [3] believed the Sillery to be the youngest 

 of the formations present, and correlated it with the Upper 

 Silurian "Shawangunk or Oneida conglomerate" of 

 New York. 



In 1857, James Hall [4] reported on the graptolites of 

 Point Levis, and referred the shales containing them to 

 the Hudson River group. Billings then took up the study 

 of the fossils found in the conglomerates at Point Levis, 

 and Logan [5] announced in i860 that Billings had iden- 

 tified these fossils as of Chazy and Calciferous (Beekman- 

 town) age, and that, therefore, the Levis strata belong 

 at the base of the Lower Silurian. In this paper the 

 term Quebec group was first used and the course of the 

 Champlain-St. Lawrence fault outlined. Marcou, [6] 

 in 1862, took exception to the views of Logan, and corre- 

 lated the strata at Point Levis with the Georgia shales 

 (Lower Cambrian) of Vermont. Marcou explained the 

 appearance of younger fossils in the conglomerates on 

 the basis of Barrande's doctrine of colonies. 



Billings, [7] replying to Marcou in 1863, paralleled the 

 strata of the fossiliferous part of the Quebec group with 

 those of the Llandeilo of England and Australia, and the 

 Calciferous and Chazy of America. 



