[AMI] GEOLOGY OF SOME CITIES IN EASTERN CANADA 163 
which were deposited by that great glacier whose centre of accumula- 
tion and dispersion was in the Labrador Peninsula to which the name 
“ Labradorean Glacier” has been applied. 
The term Labrador formation is here introduced to designate that 
sheet of “till” or “boulder clay” formed and deposited by the 
Labradorean glacier. The general trend of that glacier in this portion 
of Canada was north-east to south-west with local variations due to the 
peculiar orographic features of the Island of Montreal. 
No fossil organic remains have as yet been detected in these boulder 
clays or glacial deposits which vary in thickness (owing to subsequent 
denudation) from 0 to a few inches, to upwards of 100 feet. Along 
the Lachine canal, and the surrounding flats to the west ,of Montreal, 
and eastward to Hochelaga, boulder clays form conspicuous feature of 
the surface geology, and may be easily recognized by te presence of 
glaciated materials. 
The Champlain formation.—This formation is Patol: into two 
series: one a marine clay, the other a marine sand formation. The 
“ Leda clay” appears to occupy the lower levels of the valley of the St. 
Lawrence immediately overlying the boulder or glacial clays of the 
Labrador formation, and forms raised beaches and terraces of blue clay 
in which minute shells of the genus Leda, L. (Portlandia) arctica, Gray, 
occur; which shell has given the name to the formation. These clays 
vary from a few inches in thickness to several feet, reaching fifty feet 
in certain localities, and also carry boulders disseminated throughout 
the mass. They are for the most part bluish-gray, fine-grained, more or 
less plastic or stiff clays and muds, at times dark brown and black, as at 
the Tanneries, and hold both vegetable and animal remains in a fos- 
silized condition. Amongst these may be mentioned :—Leda (Port- 
landia) arctica, Craniella Logani, Ophioglypha Sarsii, Polystomella 
crispa, and many other foraminifera. 
The Saxicava sand formation, also called “ Montreal Saxicava 
sand” by Sir William Logan in his “ Map showing the distribution of 
various superficial deposits between Lake Superior and Gaspé,” issued 
in 1865, by the Geological Survey of Canada, when he was director, 
which term might well be adopted in the nomenclature of Canadian 
Pleistocene formations for the St. Lawrence and Ottawa valleys, con- 
sists for the most part of light yellow and ferruginous sands immediately 
overlying: the Leda clay of which it may be considered in a perfectly 
logical way as the littoral or shore deposit. It varies in thickness from 
a few inches to several feet and is marked by the presence of Saxicava 
rugosa, Mya arenaria, M. truncata, Macoma fragilis,.Macoma calcarea. 
Sec. IV., 1900. 9. 
