258 ITS EARLY INFLUENCE. 



deaux and Touraine, had its development. Like 

 influences may be traced still further back in time, 

 as into the Nummulitie period; in no other way 

 than by the action of cross Atlantic currents can 

 the western relations of certain forms found in 

 both of these assemblages be satisfactorily ac- 

 counted for. 



The waters of the equatorial current raise the 

 temperature of the central regions of the Northern 

 Atlantic ; and, from the prevalence of westerly and 

 south-westerly winds, they thus, indirectly, influence 

 the climate of north-western Europe ; but, as a 

 general rule, these heated waters do not now come 

 into immediate contact with our shores — they are 

 separated from them by a broad interval of sea, at 

 a much lower temperature. 



The removal of the land separating the Arctic 

 basin from the North Atlantic, not only had the 

 effect of lowering the temperature of the waters of 

 the whole of that area, but, by the set of the 

 oceanic currents which were forthwith established, 

 the Arctic fauna became diffused along the whole 

 of that Atlantic coast of Europe. The change was 

 sufficient to extinguish — locally, at least — three- 

 fourths of the previous fauna, as it had existed on 

 the coasts of France and Spain, and it was at that 

 time that the commingling of northern forms com- 

 menced, which has resulted in the present complex 

 character of the marine fauna of our Mediterranean 

 and mid-European regions. 



