Animal Nature of Eozobn Canadense. 473 



I confess that in the intervening time I have seen no 

 good reason to induce me to doubt the essential validity 

 of the work embodied in this paper of 1865, or to modify 

 to any considerable extent the conclusions therein stated. 

 On the other hand, many new and confirmatory facts 

 have been disclosed, and after careful and, I trust, candid 

 study of the objections raised, down to those which have 

 recently appeared in the Dublin Transactions, I believe 

 that they largely depend on the want of knowledge of the 

 character of the Grenville formation, and on misapprehen- 

 sion as to the form and structure of Eozoon and its mode 

 of occurrence- 

 It is true that in those members of the Laurentian 

 system of Logan which are below and above the Grenville 

 Series, later observations have not only failed to detect 

 fossils, but have shown valid reasons adverse to the prob- 

 ability of their occurrence, at least in the portions of those 

 formations hitherto open to our study. 1 



The lowest Laurentian gueiss of Logan (Trembling 

 Mountain gneiss, Ottawa gneiss, fundamental gneiss),which 

 occupies a vast area in Northern Canada, 2 and is the only 

 part of the system known to many geologists, consists, so 

 far as known, wholly of foliated or massive orthoclase 

 gneiss, with bands of hornblendic schist (amphibolite), and 

 of hornblendo-micaceous schist. While in some places it 

 appears to have a truly bedded structure, especially where 

 different varieties of gneiss, amphibolite, and biotitic schist 

 alternate, in others its foliation is obscure, or seems to 

 have been induced by heat and pressure. Dr. F. D. Adams, 

 who has given much study both to its character on the 

 large scale, and to the microscopic structure of the rocks, 

 in his latest publication on the subject 3 characterizes it as 



1 See Geological Magazine, June, 1895. 



2 Acccordiug to the geological map of Northern Canada prepared by Dr. G. M. 

 Dawson for the Geological Survey, the area of Laurantian rocks exceeds two millions 

 of square miles. Of this, so far as is known the older or fundamental gneiss occupies 

 by far the larger portion. 



3 Journal of Geologv, Vol. i, No. 4, 1893. 



