98 



POST-TERTIARY ENTOMOSTRACA. 



3. Relation of ihe Scotch glacial fauna to the glacial fauna of Canada. 



The fossil glacial fauna of Canada is not so widely distinct from the living fauna of 

 the Gulf of St. Lawrence as the fossil glacial fauna of the Clyde beds is distinct from the 

 living fauna of the Firth. 



In Scotland at least sixteen species are found fossil which are extinct in British 

 waters, together with many Arctic varieties of British species. 



In Canada Dr. Dawson has described 205 species of " Post-phocene fossils," and 

 remarks that "the whole of these, with three or four exceptions, may be affirmed to be 

 living Northern or Arctic species, belonging, in the case of the marine species, to moderate 

 depths, or varying from the littoral zone to — say 200 fathoms. The assemblage is identical 

 with that of the northern part of the Gulf of St. Lawrence and Labrador coast at present, 

 and differs merely in the presence or absence of a few more southern forms now present in 

 the Gulf, especially in its southern part, where the fauna is of a New England type, 

 whereas that of the Post-pliocene may be characterised as Labradorian."^ 



This marked contrast between the Canadian and Scotch glacial fauna in relation to 

 the fauna locally existing proves the greater completeness of the change of climate in 

 Scotland than in Canada. 



The Scotch glacial fauna has, moreover, a strong alliance with the Canadian shown by 

 the prevalence in both of very characteristic Arctic species. 



Out of thirty-three fossil species of Ostracoda collected from the Post-pliocene beds of 

 Canada and Maine, 



23 are found in Scottish glacial beds, 

 25 live in British waters, 

 6 are new. 



The comparison between the Scotch and Canadian beds is of special interest, since it 

 suggests that at the period when the glacial fauna flourished in the Scottish seas, the 

 climate was nearly the same as that prevaihng in Canada during the same epoch, i. e. 

 slightly colder than that of the St. Lawrence. 



The fossils, however, must not be considered as marking the extreme point of cold 

 reached during that epoch ; but rather as indicating the commencement of slightly 

 milder conditions than had hitherto prevailed. 



The question suggested by this comparison, therefore, is, What conditions would 

 produce in the Clyde a temperature slightly colder than that of the Gulf of St. 

 Lawrence ? 



^ ' Notes on the Post-pliocene Geology of Canada,' by J. W. Dawson, LL.D. ; Montreal, 1872 ; p. 101. 



