* 
208 The American Naturalist. [February, 
beds, and areas of boulders. Erratics remarkable for size, position, 
etc. Climate and fauna in post-Pliocene times. The paper was 
illustrated by photographs and diagrams. 
THE STRUCTURE AND ORIGIN OF GLACIAL SAND PLAINS. William M, 
Davis, Cambridge, Mass.—Sand Plains are delta-like deposits of strati- 
fied gravel and sand, formed in bodies of standing water at the margin 
of the melting ice of the last glacial epoch. Their growth was rapid 
compared to the backward melting of the ice-front, and the pits in 
their surface mark the location of isolated blocks of ice, which their 
sands surrounded, 
NOTE ON THE PRE-PALAOZOIC SURFACE OF THE ARCHAAN TERRANES 
or CANADA. Andrew C. Lawson, Ottawa, Canada.—Observations 
along the northern limit of the Palzozoic show that the surface of the 
Archean was, at the time of the deposition of Cambrian or earlier 
formations, to a large extent as hummocky and roches moutonnées as it 
is to-day. Hence this feature cannot, as it is generally supposed, be 
due to conditions of glacial epoch except to a very limited extent. 
Slight reduction of the Archzan surface since early Palaeozoic, but 
enormous previous denudation. Origin of material of post-Archzan 
formation. 
GLACIAL FEATURES OF PARTS OF THE YUKON AND MACKENZIE 
Basins. R. G. McConnell, Ottawa, Canada.—This paper contains 
a brief description of the glacial deposits observed along the Liard 
and Mackenzie Rivers, and includes notes on the silting up of a 
southern arm of Great Slave Lake, on the height of Erratics along 
the eastern flanks of the Rocky Mountains, on the absence of Boulder 
Clays from the valleys of the Porcupine and the Yukon, and on the for- 
mer existence of a great lake at the confluence of these two streams. 
REMARKS ON THE SURFACE GEOLOGY or ALasKa. I. C. Russell, 
Washington, D. C.—The writer wishes to call attention to, first, the 
formation of the Tundra ; second, to the absence of residual clays and 
other evidences of rock decay and the absence of glacial records along 
the Yukon and Porcupine Rivers in Alaska. 
Post-TERTIARY DEPOSITS ON MANITOBA AND THE ADJOINING TERRI- 
TORIES OF CANADA. J. B. Tyrrell, Ottawa, Canada.—The area 
stretching from the Archean nucleus in the eastern portion of Mani- 
toba, to near the foot of the Rocky Mountains, has, in preglacial 
times, had a very irregular surface, which was planed by the passing 
of the continental glacier, and the irregularities filled often to great 
depth with unstratified till. This till, or ground moraine, forms the 

