1867.] DAAYSOX LArRENTIAN" FOSSILS. 263 



organic forms ; but their rhombic or hexagonal outline when seen 

 in cross section, their transverse cleavage-planes, and their want of 

 any definite arrangement or relation to any general organic form 

 are sufficient to undeceive any practised observer. I have not seen 

 specimens of the metaxite from Reichenstein referred to by Messrs. 

 King and Eowney ; but it is evident, from the description and figure 

 given of it, that, whether organic or otherwise, it is not similar to 

 the canals of Eozoon C'anadense. But all these and similar compa- 

 risons are evidently worthless when it is considered that they have 

 to account for definite, ramifying, cylindrical forms, penetrating a 

 skeleton or matrix of limestone, which has itself a definite arrange- 

 ment and structure, and, further, when we find that these forms are 

 represented by substances so diverse as serpentine, pyroxene, lime- 

 stone, and carbonaceous matter. This is intelligible on the suppo- 

 sition of tubes filled with foreign matters, but not on that of dendii- 

 tic 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 speci- 

 mens, 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, com- 

 posed of the broken fragments of similar laminated structures. 

 Purther, much of the apparently acervidine Eozoon rock is composed 

 of such broken fragments, the interstices between which should not 

 be confounded with the chambers ; while the fact that the serpen- 

 tine fills such interstices as well as the chambers shows that its 

 arrangement is not concretionary*. Again, these chambers are 

 filled in different specimens with serpentine, pyroxene, loganite, cal- 

 careous 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 Rowney, has obliged 

 them to admit that the laminated forms in combination with the 

 canal-system are " essentially 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 in- 

 stance, in those of Bavaria and Scandinavia) Carpenter and Giimbel 

 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. Giimbel, whose paper is well de- 

 serving of study by aU 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 



* I do not include here the " septariiform " structure referred to above, wliich 

 is common in the Canadian serpentine and has no connexion with the forms of 

 the chambers. 



