140 JOURNAL OF CONCHOLOGY, VOL. II, NO. 5, JANUARY, I905. 



over a former land-connection which may have joined them to the 

 continent, rather than by an accidental or occasional means of 

 distribution. But it is also possible that some species may have 

 originated in the British Islands. We know from Messrs. Kennard 

 and Woodward's^ researches, that at least twenty-seven species of our 

 present land and freshwater fauna already inhabited these islands in 

 Pliocene times, and one hundred and six during the later Pleistocene 

 period. To judge from the presence in caves of the remains of such 

 large creatures as the Mammoth and the Irish Elk in both England 

 and Ireland, we must conclude that the British Islands were joined 

 to the continent in recent geological times, during which the cave 

 deposits were formed. No necessity, therefore, appears to exist for 

 the assumption that any considerable number of our land and fresh- 

 water mollusca colonized these islands by the difficult and hazardous 

 method of crossing the ocean, when they could do so more conveni- 

 ently by means of a land-passage. 



Edward Forbes, who was one of the first naturalists to study the 

 subject of the origin of the British fauna, laid down his views in a 

 very remarkable and fascinating memoir.^ In it he expresses the 

 opinion that the British Islands have acquired their fauna and flora 

 by colonization from another neighbouring land, or from several, 

 previous to isolation, and that the greater part of the animals and 

 plants have migrated to our area over continuous land before, during 

 and after the Ice Age (p. 65). The great mass of our pulmon- 

 iferous molluscs are believed by Prof Forbes to have arrived during 

 the Post-Pliocene period, i.e., in Pleistocene times from the Germanic 

 regions of the continent (p. 9). But these species, he says, are 

 deficient westward — in Ireland, for instance, the migration of those 

 less speedy of diffusion, which are now peculiar to England, having 

 been arrested by the breaking-up of that land passage which connected 

 England with Ireland. A little earlier in the history of the British 

 Islands there occurred, according to Prof Forbes, an incursion of 

 northern animals and plants, transported to our area by floating ice 

 from the north, and stranded on mountains which appeared as islands. 



More ancient still is his Kentish fauna, which includes such species 

 as Helix poffiatia, H. obvohita, H. cartusiana, Clmisilia ventricosa, and 

 Buliminus montanus. The Devon fauna is another and yet older 

 fauna and more southern in character. Prof Forbes remarks that it 

 is well seen in the south-east of Ireland, Helix pisana being a mol- 

 luscan representative. 



1 Kennard, A. S., and Woodward, B. B., "The Post-Pliocene Non-Marine Mollusca 

 of the South of England," Proc. Geologists Association, vol. 17, 1901. 



2 Forbes, E., "On the connection between the Distribution of the existing Fauna and 

 Flora of the British Isles and the Geological Changes which have effected their Area, especially 

 during the Epoch of the Northern Drift," Memoir Gcol. Survey, vol. i, 1846. 



