1867.] CROSSKEY — ON GLACIAL DEPOSITS. 211 



J. Gwyn Jeffreys considers a specimen from Quebec to which that 

 name has been affixed to be Scalaria borealis. Taking the contents 

 of one section, as collected by Dr. Dawson (this journal, April, 

 1865), out of twenty species of Lamelli-branchiata, fifteen occur 

 fossil in Scotland, and seventeen out of twenty-seven species of 

 Gasteropoda. 



Speaking generally, about two-thirds of the Scottish fossils at 

 present collected are also fossil in Canada, while the differences are 

 no greater than those which geographical position might easily 

 cause. At the period, therefore, when our glacial fossils lived in 

 the Scottish seas, the climate was nearly the same as that prevail- 

 ing in Canada during the same epoch — that is, slightly colder than 

 in the present Gulf of St. Lawrence. The fossils, however, can not 

 be considered as marking the extreme point of cold reached during 

 the epoch, but rather as indicating the commencement of slightly 

 milder climatic conditions than had hitherto prevailed. When the 

 deposition of the oldest boulder clay commenced (which it must 

 always be remembered is beneath the shell beds in the Clyde 

 sections), the land must have stood higher than at present, and the 

 temperature would be more intense than during its subsidence. 



The question of climate as indicated by the fauna, thus resolves 

 itself into this — what conditions would produce in the Clyde a 

 temperature slightly colder than that of the Gulf of St. Lawrence ? 



The existence of an arctic current, the wide expanse of land in 

 the American Arctic regions, exercising its chilling influence, and 

 other circumstances connected with the directions of the mount a in 

 ranges and heights of the watershed, well known to the physical 

 geographer, sufficiently account for the climate of Canada. A 

 corresponding series of circumstances, therefore, would adequately 

 explain the existence of a more arctic climate in Scotland. There 

 is no necessity to introduce causes for the production of cold which 

 do not now exist. Those alterations of level, for which there is 

 ample evidence, would involve re-arrangements of the relative 

 proportions of land and water, and vital changes in the directions 

 of the arctic currents. For the solution of the problems involved 

 in the great history indicated by the fossil fauna of Canada and 

 Scotland, we must first consult those great principles of physical 

 geography, which may now be studied in hourly action over the 

 surface of the globe. From Transactions of the Geol. Society of 

 Glssgow. 



