254 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



Grenville. From the village of Madoc, the zone of limestone which 

 has been particularly alluded to runs to the eastward on one side of 

 the trough, in a nearly vertical position into Elzivir, and on the other 

 side to the northward, through the township of Madoc into that of 

 Tudor, partially and unconformably overlain in several places by 

 horizontal beds of Lower Silurian limestone, but gradually spreading, 

 from a diminution of the dip, from a breadth of half a mile to one 

 of four miles. Where it thus spreads out in Tudor it becomes 

 suddenly interrupted for a considerable part of its breadth by an 

 isolated mass of anorthosite rock, rising about 150 feet above the 

 general plain, and supposed to belong to the unconformable Upper 

 Laurentian, thus showing that the specimens of Eozoon of this 

 neighbourhood, like those previously discovered and described, be- 

 long to the Lower Laurentian scries. 



The Tudor limestone is comparatively unaltered ; and, in the spe- 

 cimen obtained from it, the general form or skeleton of the fossil 

 Cconsisting of white carbonate of lime) is imbedded in the limestone 

 without the presence of serpentine or other silicate, the colour of 

 the skeleton contrasting strongly with that of the rock. It does 

 not sink deep into the rock, the form having probably been loose 

 and much abraded on what is now the under part, before being 

 entombed. On what was the surface of the bed, the form presents 

 a well-defined outline on one side ; and in this and the arrangement 

 of the septal layers it has a marked resemblance to the specimen 

 first brought from the Calumet, eighty miles to the north-east, and 

 figured in the ' Geology of Canada,' p. 49 ; while all the forms from 

 the Calumet, like that from Tudor, are isolated, imbedded specimens, 

 unconnected apparently with any continuous reef, such as exists at 

 Grenville and the Petite Nation. It will be seen, from Dr. Dawson's 

 paper, that the minute structure is present in the Tudor specimen, 

 though somewhat obscure ; but in respect to this, strong subsidiary 

 evidence is derived from fragments of Eozoon detected by Dr. Daw- 

 son in a specimen collected by myself from the same zone of lime- 

 stone near the village of Madoc, in which the canal-system, much 

 more distinctly displayed, is filled with carbonate of lime, as quoted 

 from Dr. Dawson by Dr. Carpenter in the Journal of this Society for 

 August 1866. 



In Dr. Dawson's paper mention is made of specimens from Went- 

 worth, and others from Long Lake. In both of these locahties the 

 rock yielding them belongs to the Grenville seam, or uppermost of the 

 three great bands of limestone heretofore described as interstratified 

 in the Lower Laurentian series. That at Long Lake, situated about 

 twenty-five miles north of Cote St. Pierre in the Petite-Nation Sig- 

 niory, where the best of the previous specimens were obtained, is 

 in the direct run of the limestone there ; and like it the Long-Lake 

 rock is of a serpentinous character. The locality in Wentworth 

 occurs on Lake Louisa, about sixteen miles north of east from that of 

 the first Grenville specim-ens, from which Cote St. Pierre is about 

 the same distance north of west, the lines measuring these distances 

 running across several important undulations in the Grenville band 



