Sir W. E. Logan on the Fauna of the Quebec Rocks. 219 
coasts the north side of the Island of Orleans, leaving a narrow 
margin on the island for the Hudson River or Utica formation. 
From near the east end of the island it keeps under the waters 
of the St. Lawrence to within eighty miles of the extremity of 
aspé. Here again it leaves a strip of the Hudson River or 
Utica formation on the coast. 
To the southeast of this line the Quebec group is arranged in 
long narrow parallel synclinal forms with many overturn dips. 
These synclinal forms are separated from one another on the 
main anticlinals by dark grey and even black shales and lime- 
stones. These have heretofore been taken by me for shales and 
limestones of the Hudson River formation, which they strongly 
resemble, but as they separate the synclinals of the Quebec group 
must now be considered older. I am not prepared to say that 
the Potsdam deposit in its typical form of a sandstone is any- 
where largely developed above these shales, where the shales are 
in greatest force. Neither am I prepared to assert its absence, 
as there are in some places masses of granular quartzite, not far 
temoved from the magnesian rocks of the Quebec group, which 
require farther investigation; but, from finding wind-mark and 
Npple-mark on closely succeeding layers of the Potsdam sand- 
stone where it rests immediately upon the Laurentian series, we 
know that this arenaceous portion of the formation must have 
been deposited im mediately contiguous to the coast of the ancient 
Silurian sea, where part of it was even exposed at the ebb of 
tide. Out in deep water the deposit may have been a bl 
artially calcareous mud, such as would give the shales and 
mestones which come from beneath the Quebec group. 
Canada no fossils have yet been found in these shales, but 
the Shales resemble those in which Oleni have been found in 
Georgia (Vermont). These shales appear to be interp - 
tween eastward dipping rocks equivalent to the magnesian strata 
of the Quebec group, and they may be brought up by an over- 
lapping anticlinal or dislocation. We are thus led to believe 
that these shales and limestones, which may be subordinate to 
- the Potsdam formation, will represent the true primordial zone 
in vate pe 
t. Murray has this season ascertained that the lowest rock 
that is well Shaniceacod by its fossils in the neighborhood of 
Sault Ste. Marie, near Lake Superior, really belongs to the 
= ye‘and Black River group, and that it rests on the sand- 
Stones of Ste. Marie and Lacloche, the fossiliferous beds at the 
Alter place being tinged with the red color of the sandstone 
immediately below them. These underl 
1 Vivalent to the Quebec group and the black colored shales 
