THE FAUNA OF BRITAIN. \2J 



is merely meant to give a general idea of the manner 

 in which the great northern sea moved westward and 

 slowly covered a large portion of the British Islands. 

 These peculiar geographical conditions explain, I 

 think, better than anything, the absence from parts 

 of the Midlands and the north of England of 

 such a number of terrestrial invertebrates which 

 are otherwise widely distributed over the British 

 Islands. In spite of the fact that a large portion 

 of the British Islands became submerged, we 

 possessed at that time an extensive area which 

 has since been claimed by the sea, so that there 

 was ample room for the present fauna to survive 

 the Glacial period. The climate during this period 

 was probably much the same as it is at present, 

 though moister, with cooler summers and milder 

 winters. 



It may be asked what proof we have of such an 

 extensive submergence of England and Ireland. My 

 own views are principally based on the general 

 distribution of the fauna in the British Islands, and 

 the belief that nothing but a mild climate during 

 the Glacial period could have brought it about. On 

 purely geological grounds, however, some geologists, 

 notably Mr. Mellard Reade, have come to a similar 

 conclusion. " The whole of Lancashire and Cheshire," 

 he remarks (a, p. 542), " from sea-level up to about 

 400 feet, and in places 600 feet, is covered by a 

 continuous mantle of boulder-clay and sands." 

 " These clays, as a rule, contain distributed through 



