288 HISTORY OF THE EUROPEAN FAUNA. 



fauna and flora in the third chapter, I have already 

 referred to the distinguishing characters of the Lusi- 

 tanian migrants and to their distribution. I need 

 only repeat, therefore, that these are now principally 

 confined to the south-western portions of the British 

 Islands. The late Edward Forbes was the first to 

 trace the Lusitanian flora to its native home. In his 

 classical memoir on the geological relations of the 

 existing fauna and flora of the British Isles, he laid 

 the foundations of a new method of research. We are 

 as yet only beginning to realise the far-reaching 

 conclusions obtainable by a careful study of the 

 geographical distribution of animals and plants, 

 though the lines of investigation were indicated 

 by him more than fifty years ago. Forbes was 

 of opinion that the Lusitanian element in the British 

 flora was of miocene age, and that it survived the 

 Glacial period on a now sunken land to the south- 

 west of Ireland. Mr. Carpenter and myself agree 

 in so far that we are both inclined to look upon 

 this Lusitanian flora and the accompanying fauna 

 in Ireland as of pre-glacial origin. But I am 

 not quite satisfied that the Lusitanian migration 

 ceased to come north then. It may have received 

 a temporary check ; but the presence, for instance, 

 of the Dartford Warbler {Melizophilus undatus) in 

 the south-east of England would seem to indicate 

 that its northward migration took place in very 

 recent times. It is possible also that the very 

 restricted occurrence of the Dartford Warbler may 



