4 
BULLETIN OF THE NATURAL HISTORY SOCIETY. 
under thousands of feet of the deposits of later periods; but this 
tendency of elevation has prevailed and brought them repeatedly 
to the surface. 
The structure of this Eaurentian terrane in the lower part 
is confused and obscure, but its upper part has a clear succession 
of limestones, quartzites and gneisses, which together form the 
“ Upper Series” so called, and exhibit a succession of strata and 
of changes in the sedimentation, quite as distinct as those which 
are found in later formations. Organic remains are rare in the 
fragmental sediments, for there are only a few worm burrows 
and other indications of the presence of marine animals in the 
quartzites and a few strap-like fossils in the silicious mud rocks. 
In the limestone, however, are reefs of that peculiar calcareous 
organism, Archoeozoon (apparently allied to the “ Layer Corals”) 
to proclaim the existence of organic life at this dawning time in 
the world’s history. Fossils of this type are known only from 
the oldest Palaeozoic rocks — and these more ancient ones — and 
this particular genus only in strata that are Pre-Cambrian. 
The physical history of these old sediments and the changes 
they have undergone are of intense interest to the thoughtful 
observer, as they lead us back to the very dawn of geological 
history. 
Even before Huronian time this great formation had under- 
gone important dynamical changes, had been deeply buried in 
the earth’s crust, and had been injected with extensive masses 
of syenite and quartz-diorite, which now separate the limestones 
into isolated basins. In many of these igneous masses the horn- 
blende has been chloritized, and sometimes we find the diorite 
dykes that cut this system converted into serpentine, showing 
that the whole mass of these rocks had been steeped in heated 
waters, and their anhydrous constituents changed to hydrated 
compounds, long before Cambrian times. 
In the island of Cape Breton, areas of rocks of this system, 
known as the George R. limestones, are found, some of which 
show even less change by metamorphism than those on the north 
side of the Bay of Fundy. They show a similar banded appear- 
ance in gray and dark gray colors, parallel to the bedding, and, 
