296 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



by the Silurian and Devonian Series in this region. The 

 rock of either age almost everywhere approaches the sur- 

 face and is covered with a few inches of vegetable mould. 

 Where fires have occurred the soil is burned away and the 

 bare surface exposed. Very few areas of drift were seen, 

 the most imposing being some low hills on St. Martin 

 Lake. Denuding forces appear to have cut down the 

 surface of the country to one nearly uniform level from 

 the Eiding Mountain ranges to the Laurentides. The 

 upper extremity only of this excavated valley being 

 covered many feet deep with quaternary deposits through 

 which Eed Eiver, the Assinniboine and White Mud Eiver 

 have cut their channels. 



The uninterrupted continuity of the rim of the Devonian 

 rocks through the United States, Canada, Eupert's Land 

 and the valley of Mackenzie Eiver can scarcely be doubted. 

 Its outcrop from the Atlantic to the Arctic Ocean 

 would extend over sixty degrees of longitude and thirty 

 degrees of latitude. The Devonian rocks in the valley of 

 the Mackenzie Eiver have many characteristics in common 

 with those of Lake Winnipeg. 



[The following are the fossils from Snake Island in Lake 

 Winnipego-sis. 



Atrypa reticularis (Linne) in abundance, both the com- 

 mon form with moderately coarse ribs and the more finely 

 striated varieties, Atrypa aspera (Schlotheim). The speci- 

 mens very closely resemble those figured by Professor 

 Hall, in his new work, the " Geology of Iowa," plate vi. 

 figs. 3, a, c, d, but are a little more pointed in front. A 

 fine Orthis agrees well with the figures and descriptions 

 of 0. lowensis, (Hall,) Geology of Iowa, plate ii. fig. 4, 

 but is a little longer. The proportions are the same, but 

 the length, breadth and depth are each two lines greater 

 than the figures. Besides these there are fragments of 



