THE FAUNA OF BRITAIN. 125 



the same species recurring again on the south-west 

 coasts of England and Ireland, thus clearly indicating 

 a former continuity of coast-line between these points, 

 now separated by deep sea. A very familiar example 

 to British zoologists is the purple rock-boring Sea- 

 urchin {Strongylocentrotus lividus), but there are a 

 great many others, such as the semi-marine Beetles 

 Octhebiiis Lejolisii and dEpophilus Bonnairei^ the 

 Crustaceans Achceus Cranchii, Inachus leptochirus, 

 Gonoplax angulata, T/iia assidua, Callianassa sub- 

 terranea y the Fishes Blennius galerita and Lepado- 

 gaster Decandollii^ and the Molluscs Otina otis, 

 Donax politus, and Amphidesma castaneum. 



Before concluding this chapter, a few words as to 

 my views on the conditions prevailing during the 

 Glacial period will not be out of place. They do not 

 differ very much from those held formerly by most 

 geologists; and even at present there are, as I have 

 mentioned before, a few upholders of those older 

 views. 



The sea, I think, must have gradually crept across 

 England from the east during, or shortly after, the 

 Forest-Bed period, so as to separate the south from 

 the north, whilst Ireland and Scotland were then still 

 connected with one another. At a later stage, the sea 

 also partially invaded Ireland, and this condition is 

 very roughly represented on the accompanying map. 

 Mr. Kendall kindly drew my attention to the fact 

 that several notable areas on which shelly drift has 

 been observed are here placed upon the land; but 



