Clare Island Survey — Aquatic Coleoptera. 29 15 



fact that in other groups the same tendency is noticeable. It has been 

 accounted for on the ground that these western species are a remnant of the 

 pre-Glacial fauna and flora, the northern species having come southward with 

 the Glacial period, the southern having come northward at an earlier date. 



The statements in either direction are at present most unconvincing. 

 Bulman 1 for instance points out that " Ice-sheets and glaciers terminate in 

 temperate latitudes so that a temperate fauna would be in close proximity to 

 ice, as in Switzerland, the Himalayas and America," and he suggests that the 

 British fauna was not exterminated during the Glacial period, but only some- 

 what reduced. Scharff 2 produces evidence to show that the Ice Age was a 

 much less severe period than is generally supposed and he also accommodates 

 the bulk of the present fauna and flora in our islands during that period. 

 This view undoubtedly has the advantage of being able to account for the 

 comparative abundance of mammals, a group which, however easily the rest 

 of the fauna and the flora might be transported can scarcely have reached 

 our area after that became separated from the continent, and although there 

 seems to be great differences of opinion with regard to when that separation 

 took place, the majority of geologists seem to favour the view that it happened 

 during or about the time of the Glacial period. 



On the other hand, Clement Beid 3 regards any survival of our flowering 

 plants, except in the case of a few arctic and alpine species, as quite 

 impossible. He mentions the discovery in alluvial deposits of south Devon- 

 shire almost at sea-level, of leaves of the dwarf arctic birch and some arctic 

 mosses as indications of the severity of the Glacial climate and also refers to 

 evidence of floating ice in the English Channel. His views are supported 

 also by the work of Lewis on the Scottish Peat-mosses 4 who finds evidence 

 that the first flora on the Glacial deposits consisted of arctic species such as 

 Dryas octopetala. 



But even many of those who recognize the arctic nature of the fauna and 

 flora of the Glacial period consider that the southern and western Irish group 

 is pre-Glacial and apparently follow Edward Forbes 5 in regarding it as having 

 reached our area during or before the Miocene period. Forbes, however, 



1 " The Effect of the Glacial Period on the Fauna and Flora of the British Islands." Nat. Sci., iii 

 1S93. 



2 " The History of the European Fauna," 1899, p. 65, et seq. 



3 " The Relation of the Present Plant Population of the British Isles to the Glacial Period." 

 Brit. Assoc, Section K, Portsmouth Meeting, 1911. 



4 Trans. Roy. Soc. Edinh. :— xli, Part iii, 1905 ; xlv, Part ii, 1906 ; xlvi, Part i, 1907 ; xlvii, 

 Part iv, 1911. 



5 " The Geological Relations of the Fauna and Flora of the British Isles," &c. Mem. Geol, 

 Survey, vol. I. 1846. 



