112 Dr. J. W. Dawson—Canadian Pleistocene. 
submarine accumulation by the unoxidized and unweathered con- 
dition of its materials. ‘he strive beneath it, and the direction of 
transport of its boulders, show a general movement from N.E. to 
S.W., or up the St. Lawrence Valley from the Atlantic. Connected 
with it, and apparently of the same age, are evidences of local 
glaciers denuding into the valley from the Lawrentian highlands. 
The Boulder-clay of the basins of the great lakes, and of the 
western plains, and of the Missouri Coteau and its northern exten- 
sions, seems to be of similar character. The basins of the lakes are 
parts of old Pliocene valleys dammed up with Pleistocene debris.’ 
The Missouri Coteau and its extensions, probably the greatest moraine 
in the world, and the “terminal moraine” of the great continental 
glaciers of some American geologists, appears to be the deposit at 
the margin of a sea laden with vast fields of floating ice.’ 
The Lower Leda Clay (d) seems in all respects similar to the 
deposits now forming under the ice in Baffin’s Bay and the Spitz- 
bergen Sea. The Upper Leda Clay represents a considerable amelio- 
ration of climate, its fauna being so similar to that of the Gulf of 
St. Lawrence at present that I have dredged in a living state nearly 
all the species it contains, off the coasts on which it occurs. Land 
plants found in the beds holding these marine shells are of species 
still living on the north shore of the St. Lawrence, and show that 
there were in certain portions of this period considerable land sur- 
faces clothed with vegetation. The Upper Leda Clay is probably 
contemporaneous with the so-called inter-glacial deposits holding 
plants and insects discovered by Hinde on the shores of Lake 
Ontario.2 On the Ottawa it contains land plants of modern Canadian 
species, insects and feathers of birds, intermixed with skeletons of 
of Capelin and shells living in the Gulf of St. Lawrence. 
The changes of level in the course of the deposition of the Leda 
Clays must have been very great; fossiliferous marine deposits of 
this age being found at a height of at least 600 feet, and sea-beaches 
at a much greater elevation, while at other times there must have 
been large land areas and even fresh-water lakes. Littoral gravels 
and sands of this period may also be undistinguishable, except by 
their greater elevation, from those of the Saxicava sand. I have 
recently described the bones of a large whale (Megaptera longimana) 
from gravel north of the outlet of Lake Ontario and 420 feet above 
the level of the sea, which is not improbably contemporaneous with 
the Leda Clay of lower levels, and much higher than deposits near 
Lake Ontario regarded as of lacustrine origin.* These changes of 
1 Newberry, Reports on Ohio; Hunt, Canadian Reports; Spencer, Ancient Out- 
let of Lake Erie, Ann. Phil. Society, 1881. 
2 Report on 49th Parallel, G. M. Dawson. 
3 Proceedings of Canadian Institute, 1877. Dr. Hinde in this paper incorrectly 
states that the Leda Clay belongs to the ‘‘close of the Glacial Period,”’ and that 
boulder drift is not found above it. In truth, as Admiral Bayfield, Sir Charles 
Lyell, and the writer have shown, boulder-drift is still in progress in the Gulf and 
River St. Lawrence, though in a more limited area than in the Post-Pliocene period ; 
but any considerable subsidence of the land might enable it to resume its former 
extension. 4 Canadian Naturalist, vol. x. No. 7. 
