506 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 16, 



James's Bay (the southern extremity of Hudson's Bay), which have 

 been submitted to Mr. Salter, but not yet named, exhibit the same 

 general Upper Silurian character with those above quoted. They 

 comprise specimens of the same Corals (Favosites, Cyathophyllum^ 

 Clisiophyllum, and Favistella)^ the universal Atrypa reticularis^ 

 Pentamerus oblongus, several Spirifers and Orthidce, and an Ortho- 

 ceras. Mr. Barnston, of the Hudson's Bay Company's Service, who 

 has resided for upwards of twenty years in various parts of the 

 district under notice, and whose qualifications as an observer are 

 highly spoken of by Sir John Richardson, has traced the Silurian 

 rocks from James's Bay to Marten's Falls, near the source of Albany 

 River, at the eastern edge of the granitic plateau, which would give 

 an average breadth of about 200 miles for the formation in this part. 

 The boat-route from Lake Winipeg to York Factory crosses the 

 limestone belt at right angles to its course at Rock Portage, and its 

 breadth is there found to diminish to less than 100 miles. The ave- 

 rage width of the formation may perhaps be estimated at about 150 

 miles. 



The mineral structure of the rocks forming the northern shores of 

 America has been so fully and minutely investigated and described 

 by Prof. Jameson, Mr. Konig, Dr. Fitton, and Sir John Richardson, 

 that I shall here, as well as in the notices of the other formations of 

 this territory, confine myself exclusively to the examination of their 

 organic remains, referring the reader for every necessary information 

 on the mineralogical character of the rocks in which they are found 

 to the valuable publications of those authors. 



Silurian Basin of Lake Whiipeg. — To the westward of the plateau 

 of crystalline rocks, and following its course for a considerable 

 distance northward, lies an extensive deposit of horizontal limestone, 

 underlying the wide prairie country which extends towards the Rocky 

 Mountains. Lake Winipeg, which is situated on the line of junction 

 of the two formations, is a long and narrow sheet of water, 230 geo- 

 graphical miles long, and about 40 wide ; and, with its associated 

 lakes (Moose Lake, Muddy Lake, Winnepegoos, and Manitoba 

 Lakes), receives, through its affluents — the Saskatchewan, the Red 

 River, and other streams — a wide extent of prairie drainage. The 

 commercial route from Lake Superior up to this point lies almost 

 wholly within the granitic tract, touching on Silurian deposits only 

 at the mouth of Rainy River and at one of the south-western arms of 

 the Lake of the Woods, where Dr. Bigsby has detected a few organic 

 remains indicative of the Upper Silurian formation *. The Winipeg 

 flows wholly within the granitic district, and has the lake-like dilata- 

 tions and other characteristics of the streams which traverse the cry- 

 stalline tract. When we descend to Lake Winipeg, we come upon 

 epidotic slates, conglomerates, sandstones, and trap-rocks, which bear 

 a close resemblance to those of the mining district of Pigeon Bay on 



* The following list is given by Dr. Bigsby : a small Phacops, small Orthoce- 

 rata, minute Encrinital columns, Favosites Gothlandica, Cyathophyllum, Murchi- 

 sonia, Pentamerus Knightii, Leptcena, Avicula, Atrypa, and Spirifer, Quart. 

 Journ. Geol. Soc. vol. viii. p. 405. 



