SIR WM. E. LOGAN'S VIEWS. 381 



Chazy. Mr. Billings recognizes one species Madurea Atlantica (Billings), as belonging to the Chazy, and 

 six species as belonging to the calciferous. They are Lingula Mantelli (Billings), Camerella undescribed, 

 Ecculiomphcdus undescribed, Helicotoma uniangulata (Hall), H. perstriata (Billings), and one remarkable 

 species of an undetermined genus, like a very convex Cyrlodonla, which occurs both at Mingan and Point 

 Levi. All of the forms, particularly the trilobites, remind the observer of those figured by Dr. D. Dale 

 Owen from the oldest fossiliferous rocks of the Mississippi Valley, while independent of the six species 

 identical with Chazy and calciferous forms, there are many others closely allied to those found in the latter 

 formation in Canada. 



From the physical structure alone no person would suspect the break that must exist in the neighborhood 

 of Quebec, and, without the evidence of the fossils, every one would be authorized to deny it. If there had 

 been only one or two species of an ancient type, your own doctrine of colonies might have explained the 

 matter, but this I presume would scarcely be applicable to so many identities in a fauna of such an aspect. 

 Since there must be a break, it will not be very difficult to point out its course and its character. The 

 whole Quebec group, from the base of the magnesian conglomerates and their accompanying magnesian 

 shales to the summit of the Sillery sandstones, must have a thickness of perhaps some 5000 or 7000 feet. 

 It appears to be a great development of strata about the horizon of the Chazy and calciferous, and it is 

 brought to the surface by an overturn anticlinal fold with a crack and a great dislocation running along the 

 summit, by which the Quebec group is brought to overlap the Hudson River formation. Sometimes it 

 may overlie the overturned Utica formation, and in Vermont points of the overturned Trenton appear 

 occasionally to emerge from beneath the overlap. 



A series of such dislocations traverses eastern North America from Alabama to Canada. They have 

 been described by Messrs. Rogers, and by Mr. Safford. The one in question comes upon the boundary of 

 the Province, not over a couple of miles from Lake Champlain. From this it proceeds in a gently curving 

 line to Quebec, keeping just north of the fortress; thence it coasts the north side of the Island of Orleans, 

 leaving a narrow margin on the island of 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 

 Gaspe. 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 antidinals by dark 

 gray and even black shales and limestones. These have heretofore been taken by me for shales and lime- 

 stones 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 anywhere 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 removed from the magnesian rocks of the Quebec group, which require further investiga- 

 tion; but*, from finding wind-mark and ripple-mark on closely succeeding layers of the Potsdam sandstone 

 where it rests immediately upon the Laurentian series, we know that this arenaceous portion of the forma- 

 tion must have been deposited immediately 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 black partially 

 calcareous mud, such as would give the shales and limestones which come from beneath the Quebec group. 



In 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 interposed between eastward dipping 

 rocks equivalent to the magnesian strata of the Quebec group, and they may be brought up by an overlap- 

 ping 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 Canada. 



Mr. Murray has this season ascertained that the lowest rock that is well characterized by its fossils in the 

 neighborhood of Sault Ste. Marie, near Lake Superior, really belongs to the Birdseye and Black River 

 group, and that it rests upon the sandstones of Ste. Marie and Lacloche, the fossiliferous beds at the latter 

 place being tinged with the red color of the sandstone immediately Mow them. These underlying Lake 

 Superior rocks may thus be Chazy, calciferous, and Potsdam, and may be equivalent to the Quebec group 



