1868.] DAWSON EOZOON CANADENSE. 319 



This is intelligible on the supposition of tubes filled with foreign 

 matters, but not on that of dendritic crystallization. 



If all specimens of Eozoon were of the acervuline character, the 

 comparisons of the chamber-casts with concretionary granules 

 might have some plausibility. But it is to be observed that the 

 laminated arrangement is the typical one ; and the study of the 

 larger specimens, cut under the direction of Sir W E. Logan, 

 shows that these laminated forms must have grown on certain 

 strata-planes before the deposition of the overlying beds, and that 

 the beds are, in part, composed of the broken fragments of similar 

 laminated structures. Further, much of the apparently acervuline 

 Eozoon rock is composed of such broken fragments, the interstices 

 between which should not be confounded with the chambers ; 

 while the fact that the serpentine V\ i such interstices as well as 

 the chambers shows that its arrau o ^jient is not concretionary.* 

 Again, these chambers are filled in different specimens with ser- 

 pentine, pyroxene, loganite, calcareous spar, chondrodite, or even 

 with arenaceous limestone. It is also to be observed that the 

 examination of a number of limestones, other than Canadian, by 

 Messrs. King and llowney, has obliged them to admit that the 

 laminated forms in combination with the canal-system are 'essen- 

 tially Canadian,' and that the only instances of structures clearly 

 resembling the Canadian specimens are afforded by limestones 

 Laurentian in age, and in some of which (as, for instance, in 

 those of Bavaria and Scandinavia) Carpenter and Griimbel have 

 actually found the structure of Eozoon. The other serpentine- 

 limestones examined (for example, that of Skye) are admitted to 

 fail in essential points of structure ; and the only serpentine 

 believed to be of eruptive origin examined by them is confessedly 

 destitute of all semblance of Eozoon. Similar results have been 

 attained by the more careful researches of Prof. Gumbel, whose 

 paper is well deserving of study By all who have any doubts on 

 this subject. 



In the above remarks I have not referred to the disputed case 

 of the Connemara limestones ; but I may state that I have not 

 been able to satisfy myself of the occurrence of the structures of 

 Eozoon in such specimens as I have had the opportunity to 

 examine.* It is perhaps necessary to add that there exists in 



* Such Irish specimens of serpentine limestone as I have seen, appear 

 much more highly crystalline than the beds in Canada which contain 

 Eozoon. 



