NATURAL HISTORY, TORONTO REGION 



Spirifera duodenarius. 

 Stropheodonta demissa. 

 Conocardium cuneus. 

 Paracyclas elliptica. 

 Platyceras carinatum. 

 Proetus rowi. 



PLEISTOCENE. 

 GENERAL FEATURES. 



As previously mentioned, the greater part of the 

 region under consideration is covered with drift 

 deposits of the Pleistocene, sometimes to the thick- 

 ness of 600 or 700 feet ; and a very complex history 

 has been worked out from them. Between the 

 Devonian and the end of the Pliocene no record has 

 been preserved, but it is certain that superficial ero- 

 sion went on to a great extent in the long period of 

 dry land conditions after the middle Palaeozoic. 

 There was time to strip much of the Palaeozoic beds 

 from the Archaean floor and to cut back for many 

 miles toward the west and south the Silurian shales 

 under their protective capping of Niagara limestone, 

 thus producing the striking escarpment which crosses 

 the province. Great river valleys were carved below 

 the present level of the sea, showing that the land 

 stood higher than now, the most important beii 

 the " Laurentian River," as it has been named 

 Dr. Spencer, which drained the Upper Lakes regioi 

 through what is now Georgian Bay to the Ontaric 

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