I9I5- SCHARf'F. — The Clare hiajid Survey. 185 



freshwater sponges found by Miss Stephens in the area 

 investigated only one occurred on Clare Island. 



There is thus a general concurrence of opinion among 

 the investigators that the fresh-water fauna of the island 

 is decidedly poor as compared with that of the mainland. 

 The lack of suitable habitats may partly account for this 

 poverty, but not altogether. If we assume that the bulk 

 of the Clare Island fauna and flora reached its destination 

 by means of a land connection, the facilities for dispersal 

 of the aquatic forms may have been deficient at that time. 

 Or the poverty of the freshwater fauna may be due to quite 

 another cause. It may have been partially destroyed on 

 the island itself. No biological features are apparent which 

 would lead us to suspect such a destruction. Yet if we 

 suppose, for example, that the sea-level had stood higher 

 than it does now at any time after the arrival of the fauna, 

 many fresh -water species would have been killed as the 

 result of the serious diminution of the fresh-water area 

 on the island. Is the poverty in the fresh -water fauna due 

 to this cause ? The geological evidence may possibly 

 elucidate the problem. 



According to Mr. Hallissy, and most geologists agree 

 with him, arctic conditions set in not very long ago over the 

 whole of Northern Europe, with the result that ice -sheets 

 developed, burying the whole of Britain as far south as the 

 valley of the Thames. During the period of maximum ice- 

 development, says Mr. Hallissy, Clare Island and the Clew 

 Bay area were overwhelmed by the Central Irish glacier, 

 which invaded the district in a direction a little south of west. 

 The belief in an Ice Age, such as it is described, is prin- 

 cipally founded locally on the presence of grooves and stria- 

 tions which have been noticed on the rocks of Clare Island, 

 together with the occurrence of boulders of mainland origin 

 and of scratched stones in the Boulder-clay. Formerly 

 these phenomena were held to be due to floating icebergs 

 during a partial submergence of the Irish area. 



Mr. Hallissy does not express any opinion as to whether 

 any of the existing elements in the fauna and flora could 

 have survived these glacial conditions on Clare Island, but 



