V6 INTRODUCTION. 



ice-shroud, was warm enough to support a large number of 

 trees, shrubs, and other plants, such as inhabit the temperate 

 regions of the globe. Lastly, it has been shown, upon physi- 

 cal as well as paleeontological evidence, that the greater part 

 of the North Temperate Zone, at a comparatively recent 

 geological period, has been visited with all the rigours of an 

 Arctic climate, resembling that of Greenland at the present 

 day. This is indicated by the occurrence of Arctic shells in 

 the superficial deposits of this period, whilst the Musk-ox 

 and the Eeindeer roamed far south of their present limits. 



