6 



Life-histories of Northern Animals 



other surface materials have In most parts of our province 

 been worked up by plant and animal agencies, into a layer of 

 rich black mould. The important part played in this by the 

 Pocket-gopher is duly set forth in the chapter devoted to that 

 species. 



The Steppes of the Prairie. 



The first or lowest Prairie Steppe embraces all the Red 

 River Valley proper. It slopes from 710 feet above the sea at 

 Lake Winnipeg to nearly 1,000 feet in Minnesota. This is 



HUDSON 



THE GLACIAL 

 LAKEAGASSIZ 



The Scjuare shows present Boundries of 

 Manitoba." 



Map 2 — The Glacial Lake Agassiz. 

 Redrawn from sketch in Dr. George Bryce's paper. See foot-note 2, opposite. 



really the floor of the old Lake Agassiz, whose waters, impris- 

 oned by a great glacier to the northward, or by some other 

 cause, flooded the region and overflowed southward into the 

 Mississippi at Lake Traverse. Its western bank is the 

 escarpment known as Pembina, Riding, Duck, and Porcupine 

 Mountains. It receded by degrees owing to relative changes 

 of elevation in the land; or, as some suppose, with the melting 



