June, 1895. EOZOON AND MONTE SOMNA BLOCKS. 399 



By implication this mode of occurrence is also assumed through- 

 out the paper. The statement is, however, entirely without 

 foundation, and I am at a loss to understand whence it has been 

 derived. It certainly could not have been from any competent 

 observer who has studied Eozoon in situ. In point of fact the best 

 specimens have all been found in a thick limestone, the Grenville 

 Limestone of Sir William Logan, estimated by him at 750 feet in its 

 average thickness, though with a few intercalated thin bands of 

 gneiss and quartzite. 1 In the vicinity of Cote St. Pierre in the 

 Seigniory of Petite Nation, where some of the best specimens of 

 Eozoon are found, the outcrop of this limestone has been traced con- 

 tinuously and mapped by the Geological Survey for twenty-five miles, 

 and in the same district it occurs over an extent of more than one 

 hundred miles on the reverse sides of synclinal and anticlinal folds, 

 where it may be recognised by its character and associations as well 

 as by its holding Eozoon. 2 It is true that grains, nodules, and thin 

 interrupted bands of a white variety of pyroxene (malacolite) occur 

 sparingly in this limestone; but neither in their chemical composition 

 nor in their mode of occurrence have we any proof or even probability 

 of an igneous (intrusive) origin. This was the matured conclusion of 

 the late Dr. Sterry Hunt ; and Dr. F. D. Adams, at present our best 

 authority on these rocks, is of the same opinion. 



The Grenville limestone has been much bent and folded, and 

 with its accompanying beds has been subjected to regional meta- 

 morphism. In the Petite Nation localities, however, it has not, as 

 far as known, been invaded by igneous dykes or masses. 



The specimens of Eozoon are included in this limestone, and vary 

 from single individuals ranging from an inch to six inches in 

 diameter to aggregated groups of a foot or more ; and microscopic 

 examination shows that, in some of the beds in which they occur, there 

 are innumerable fragments showing the same structures scattered on 

 the strata planes, and associated with the minute globular chamberlets 

 which I have named Avchceosplicvina. The specimens of Eozoon may 

 be seen weathered out on the surfaces of the limestone exactly in the 

 manner of stromatopores on the surfaces of the calcareous rocks of the 

 Cambrian, Ordovician and Silurian, though I have not seen them so 

 crowded together as in some of the beds of these later formations. 



From the statements quoted from Mr. Blake (p. 274) and some 

 remarks on p. 275, I would infer that the authors possibly contemplate 

 Eozoon in an inverted position, with the acervuline part within or 



1 " Geology of Canada," p. 45. See also " Life's Dawn on Earth," and Memoir 

 on " Specimens of Eozoon Canadense." By the Author. Montreal, 1S8S. 



2 It must be evident that the singular opinion quoted on p. 277, that even these 

 great continuous Laurentian limestones may themselves have been "inclusions in 

 intrusive igneous rocks," is too monstrous to be entertained for a moment, 

 especially in opposition to the judgment of all the ablest geologists who have 

 studied them. 



