178 The American Naturalist. [February, 
Selkirks and Rocky Mountain Region of Canada, Henry M. Ami, 
Ottawa, Ont. This paper was based mainly upon a collection of Lower __ 
and Middle Cambrian fossils made by the author in the summer of 
1891. It contains notes on some eight species of Lower Cambrian 
(Olenellus zone) fossils from the gray, glossy and calcareous schists 
and limestones of the entrance to the Selkirks, some two miles west of 
Donald, British Columbia. The latter part of the paper dealt with 
the forms met with in the Middle Cambrian of Mount Stephen in the 
Rocky Mountains, near Field, B. C., where the terrane is highly fossil- _ 
iferous. Upwards of twenty species have been recorded from this 
locality, many of which are very interesting and well preserved. On | 
the Potsdam and Calciferous Terranes of the Ottawa Paleozoic Basin, 
Henry M. Ami, Ottawa, Ont. The stratigraphical, lithological and 
paleontological relations of the Potsdam and Calciferous terranes, as 3 
seen and known in the Ottawa palæozoic basin and elsewhere weredis- | 
cussed in this paper ; also the reference of these two terranes to the 
Cambro-‘Silurian or Ordovician Epoch instead of to the Cambrian 
Epoch, inferred from the internal evidence. The Criteria for the Rec- 
ognition of Separate Ice Epochs, R. D. Salisbury, Chicago, Ill.; Note 
on the Geology of Middleton Island, Alaska, George M. Dawson, a 
Ottawa, Ont. This short paper was devoted principally to the descrip- a 
tion of a boulder-clay or till from Middleton Island, which is foundto — n 
contain some marine fossils. Eskers Near Rochester, N. Y., Warren 
Upham, Somerville, Mass. The Pinnacle Hills, a very remarkable 
esker series in the southeastern suburbs of Rochester, were described | 
and attributed to deposition by a glacial river flowing between wals 
of ice and open above to the sky. Their material, which is shown " 
have been englacial, is chiefly gravel and sand, but also comprises m 
some parts very abundant and large boulders, some of which are lified 
200 feet or more above their sources within a few miles on a nearly — 
plain country. Similar explanations are also applicable to other oo 
eskers in Pittsford, several miles farther southeast. Comparison of a 
Plistocene and Present Ice-Sheets, Warren Upham, Somerville, Mas. a 
The Plistocene ice sheets of North America and Europe were compare? a 
with the now existing Malaspina, Greenland, and Antarctic ice-sheet : 
as to their areas, surface slopes and probable thickness, rates of erosioP 
and ablation, subglacial and englacial drifi, and manner of deposition a 
of various drift formations. The Malaspina glacier or ice-sheet, COW 
`. ered on its wasting borders by much drift and growing forests, we 
believed to afford explanations of forest beds between deposits fe 
till, and of the peculiar drift accumulations named drumlins, both 
