8ir W. Dawson — The Animal Nature of Eozoon. 447 



matter, mainly composed of triclinic or lime felspars, and to whicli 

 the name Anorthosite ^ may properly be applied. These rocks, 

 cutting the Grenville Series, and apparently in some places inter- 

 bedded with it, are not now regarded as a distinct series of beds, but 

 as indicating local outbursts of igneous action dating about the close 

 of the Grenville period. What aqueous rocks may have been con- 

 temporaneous with them, or may have filled the interval between 

 the Grenville Series and the Huronian, we do not at present certainly 

 know, though possibly some of the rocks associated with the upper 

 part of the Laurentian, or the lower part of the Huronian in the 

 interior, and in the eastern part of Canada, may come into this 

 place." 



It is to be observed that in 1865 these facts respecting the 

 fundamental gneiss and the Upper Laurentian of Logan, were 

 not distinctly before our minds, though in subsequent papers I 

 thought it best to consider the Grenville group as a distinct series 

 under the name " Middle Laurentian." It is quite possible, how- 

 ever, that our referring in the first instance to the Laurentian as 

 a whole, may have led to erroneous impressions. 



Fig. 2. — Topography at Cote St. Pierre, from the N.E. (For section see Dr. 

 Bonney's paper, Geol. Mag., July 1895, p. 296.) 



{a) Lower gneiss. («') The same brought forward by fold. 



[b) Limestone (Lome's Quarry), {b') The same, exposure on La Vigne's farm. 



[c) Limestone, mostly covered with soil. 



[d) Pond or small lake. 



For the purpose of these notes, therefore, it will be best and most 

 accurate to confine ourselves to the Grenville Series, which has 

 been carefully explored and mapped by the officers of the Geological 

 Survey in the country lying north of the Ottawa Eiver, and also in 

 some parts of the areas between that river and the St. Lawrence. 

 In these regions Logan recognized a thickness of 17,250 feet of 

 deposits, of which no less than 4,750 feet consisted of limestone, 

 principally in three great bands, though with intercalated gneissose 



1 Proposed by Hunt. 



2 Some of these beds are regarded by Von Hise (Amer. Journ. of Geology, vol. i) 

 as a lower member of the Huronian. They may also be identical in part with 

 the "Kewatin" group of Lawson. 



