344 PROCEEDINGS OF SECTION C. 
of pyroxene were the rocks in the ocean on which Lozodn grew ; 
but evidently this cannot be the case for the blocks are segrega- 
tion masseg and were, no doubt, formed at the same time as the 
grains of serpentine which are supposed to infiltrate the organism. 
Also, the supposed canals are sometimes filled with dolomite 
which is usually altered calcite, and is rarely deposited in cavities 
of unaltered calcite. 
The great thickness and extent of the limestones with which 
Hozobn is associated forbid the idea that they are entirely the re- 
sult of hydrothermal action on lime-bearing silicates ; but it does 
not necessarily follow that they must be organic. Also, we can 
hardly suppose the large quantities of graphite found in these 
limestones to be organically derived, for if this was the case it 
must have come from marine plants—no others being in existence 
—and as we have no knowledge of any mineral carbon-compounds 
having thus originated in large quantity in any other period, we 
should have to suppose that seaweeds were either more abundant 
or more capable of being preserved in the Archzan era than at 
any later time. The occurrence of graphite and limestone together 
suggests a common origin for both, and as we know that metallic 
carbides occur, not only in meteorites, but also in the terrestial 
iron of Ovifak in Greenland, it seems probable that both graphite 
and limestone may be due to the decomposition of calcium carbides 
by hot water. At any rate, if the officers of the Canadian survey 
are right in their ideas as to the genesis of the Grenville series, we 
cannot possibly suppose that the limestones are of organic origin, 
for no organism could have existed under such conditions.* 
HURONIAN LIFE. 
No undoubted traces of life have been found in the Huronian 
of America ; but it is probable that the Radiolarians and sponges 
discovered by Dr. C. Barrois, in Brittany, should be placed in it. 
A short account of the geological position of these fossils will be 
necessary to explain this. 
In Southern Brittany, from Finisterre to Vendée, a remarkable 
graphite-bearing quartzite is found interbedded in a series of 
gneisses and mica-schists, which cover unconformably the Lauren- 
tian fundamental gneisses of the district. Further north, in the 
Department of the Cotes du Nord, the graphitic quartzite reap- 
pears ; but here it is interbedded with phyllites and schists forming 
the series of Saint-L6, which is undoubtedly pre-Cambrian. It is 
in this graphitic quartzite, in the neighbourhood of Lamballe, that 
the fossils were found. In Southern Brittany the graphitic quartz- 
ite appears to be near the top of the system as these developed ; 
*T have not seen Dr. Mathews’ paper on Archzozoén and Sponges from the Upper 
Laurentian, near St. John, New Brunswick, in the Bulletin of the Nat. Hist. Society of New 
Brunswick ; but their organic nature has been disputed by Dr. H. Rauff, of Bonn. 
