1897] THE PROBLEMS OF BRITISH FAUNA 383 



archipelago ; central and southern Wales an island ; while the south 

 and midlands of England were joined to France by an isthmus. The 

 sea covered nearly the whole of eastern England, and stretched across 

 north Wales, and over eastern and central Ireland. Zoological 

 evidence for this transgression of the northern sea over eastern 

 Ireland is found in the distribution of the arctic marine crustacean 

 3fysis rdicta, which forms part of the ' relic fauna ' not only of the 

 Swedish lakes, but also of Lough Neagh. The sea separating 

 southern and central England from Scotland, as well as from 

 Ireland, checked the northern as well as the western progress of 

 the ' Siberian ' mammals. None of these animals are found fossil in 

 Scottish Pleistocene deposits, though the recession of the glacial sea 

 has in recent times opened a way to the north, of which the sur- 

 viving species have availed themselves. But meanwhile the isthmus 

 between Scotland and Ireland had become broken through. 



Having thus put forward a summary of Dr Scharff's views as to 

 the ages and paths of migration of the various sections of the British 

 fauna, I venture, with some diffidence, to offer a few observations 

 and suggestions. I entirely agree with Dr Scharff in considering the 

 South-western as the oldest section of our fauna, and I have no 

 doubt that it came into our area long before the Glacial Period. 

 The North American plants and animals seem to me to be more 

 ancient than Dr Scharff is inclined to admit. He classes them 

 with the general Northern fauna, but I believe that their very 

 restricted and discontinuous ranges along the extreme western margin 

 of Europe mark them as decidedly older than those northern animals 

 and plants which have a general circumpolar distribution. 



Study of the distribution of British insects shows that there is a 

 Southern fauna 1 distinct from the South-western, in that its members 

 occur generally in southern Britain, as well as in Ireland and 

 western Britain, and have a wide continental range. It is clearly 

 newer than the South-western fauna, yet the fact that it is confined 

 in Ireland to the south and west suggests that it is of considerable 

 geological age. Along the west coast of Ireland the insects of this 

 group often range some distance to the north, and their general 

 British distribution around the west and south of our islands renders 

 it likely that they held the country west and south of the area where 

 the Glacial deposits were being formed, and have, since the retroces- 

 sion of the agent which produced those deposits, been unable to 

 spread far eastwards in Ireland or northwards in Great Britain. This 

 fauna may safely be regarded as comparable to Forbes' Norman and 

 Kentish floras, and older than the Arctic fauna. As yet, however, 

 I am not prepared to accept so great an antiquity for the bulk of 



1 Examples of this group are the ground-beetles, Carnbus cancellatus and Panagaeus 

 cru.r-major, the butterflies Gonepteryx rhamni, and Leplida sinapis, and the moths Zeuzera 

 pyrina and Stauropus fagi. 



