J. W. Dawson on fossils from the Laurentian of Canada. 373 
gtown on certain strata-planes before the deposition of the over- 
lying beds, and that the beds are, in part, composed of the 
broken fragments of similar laminated structures. Further, 
much of the apparently acervuline Hozoon rock is com f 
such broken fragments, the interstices between which should not 
¢ 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, 
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 combina- 
tion 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 instance, in those of Bavaria and Scan- 
dinavia) Carpenter and Giimbel have actually found the struc- 
ture of Hozoon. The other serpentine-limestones examined (for 
. 
example, that of Skye) are admitted to fail in essential points 
= 
More careful researches of Prof. Giimbel, 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 common limestones; but I may state that I have not 
been able to satisfy myself of the occurence of the structures 
of Hozoon in such specimens as I have had the opportunity to 
| €Xamine.+ It is perhaps necessary to add that there exists in 
} Canada abundance of Laurentian limestone which shows no in- 
ation of the structures of Hozoon. In some cases it 18 €Vl- 
dent that such structures have not been present, In other cases 
ey may have been obliterated by processes of crystalliza- 
As in the case of other fossils, it is only in certain beds, 
I do not iiform” structure referred to above, which 
fecmmon in the Canadian serpentine and has no connection with the forms of 
+t Such Irish specimens of tine limestone as I have seen, appear much 
more highly erystalline than the beds in Canada which contain Eozoon. 
