VIEWS OF RICHARDSON, HUNT AND SELWYN. 457 



schists and epidotic or chloritic rocks of the mountain ranges of the interior, 

 and which, at their highest part, were also supposed to shade upward into 

 more or less perfect gneisses. It was found difficult to draw any sharply 

 defined line between this division and the underlying Lauzon. 



Richardson's later Work. — The views as to the structure of the Quebec 

 group just stated remained unchanged till 1868, when Mr. James Richard- 

 son, in the course of his explorations along the south side of the St. L'awreuce, 

 upon the evidence of certain fossils there found, advanced the theory that a 

 portion of what had been regarded as Sillery and Lauzon was in reality 

 of Potsdam age and divisible into three parts — lower, middle, and upper. 

 The rocks to which his conclusions more particularly applied embraced cer- 

 tain extensive areas of hard quartzose sandstone, with associated beds of 

 limestone conglomerate, together with slates of various colors. These he 

 considered to underlie the Levis formation, which was, however, still regarded 

 as being older than the Sillery as first established. The reasons for this 

 change of view were principally the finding of fossils of Primordial age in 

 some of the conglomerate bands, and the presence of supposed Scolithus 

 burrows in certain of the quartzose sandstones, many of which in their 

 character were supposed to resemble those of Potsdam age west of Montreal. 



This view was not very strongly supported by Sir William Logan, who, 

 upon examination of the evidence, failed to find anything which could con- 

 clusively establish their Potsdam horizon ; and subsequently the subject was 

 discussed by Dr. Selwyn, who also failed to find any sufficient reason for the 

 separation of the so-called Potsdam portion from the original Sillery sand- 

 stone. 



Hunt's later View. — In the meantime Dr. Hunt, in 1871, had propounded 

 new views as to the structure of the group, more particularly relating to the 

 supposed altered portion of the interior, in which he claimed that these 

 metamorphic rocks were not the equivalents of the fossiliferous Quebec group, 

 but belonged to an entirely distinct system, and that they should be regarded 

 as older than the Cambrian as then constituted or as a portion of the 

 Huronian, thus completely overturning the views so long maintained as to 

 their equivalency with the Sillery and Lauzon divisions. 



Sehvyn's Classification. — The study of these rocks was taken up at a later 

 date by Dr. Selwyn, then director of the Geological Survey of Canada, who 

 in 1877 first officially published the opinion that the original Quebec group 

 was divisible into three great systems, viz : (1) An upper portion, styled the 

 Lower Silurian, which comprised the Levis and Sillery (the name Lauzon 

 having been dropped) unaltered and in places fossiliferous rocks ; (2) A 

 volcanic group, probably lower Cambrian, which included quartzose sand- 

 stones, red, green, and grayish siliceous slates, serpentines and diorites with 

 dolomites ; and (3) a group composed of slaty and schistose, chloritic, mica- 



