500 Proceedinr/s of the Royal Irish Academy. 



"being carried in a direction contrary to the natural flow of a glacier, 

 if we remember that probably a strong current existed from the more 

 or less closed North European Sea to the open Atlantic. The occur- 

 rence in almost all the English boulder-clays of marine shells tells 

 strongly in favour of the view that these clays are of marine origin. 

 Moreover, they are found to contain Arctic species, and these are 

 mixed with southern forms as we approach the lands adjoining the 

 Atlantic, where an almost purely Mediterranean fauna had hitherto 

 ■existed. Arctic forms of life now found their way, not only into 

 the Atlantic, but by the newly opened Straits of Gibraltar they 

 entered the Mediterranean, and are preserved to us in some remark- 

 able deposits in Sicily. 



We liavc evidence from the St. Erth beds, to which I have already 

 had occasion to refer (p. 478). that whilst northern forms made their 

 appearance on tlie east coast of England, the fauna on the west coast 

 remained a purely southern one. This fact induced Messrs. Kendall 

 and Bell (49) to advance the liypothesis that not only were the 

 Straits of Dover closed, but that a land barrier was thrown across the 

 Atlantic from the north of Scotland to Greenland, while the St. Erth 

 beds were laid down. 



That the southern marine fauna was once continuous from the 

 west coast of Ireland to the west coast of France, soon becomes appa- 

 rent to any one who takes the trouble of studying, especially the 

 littoral animals. It is a well known fact that many shore forms 

 which occur along the west coast of Portugal and Erance reappear 

 again on the south-west coast of England, and on the south and west 

 coast of Ireland : thus clearly indicating the former continuity of 

 range now broken by the English and Irish Channels.^ 



On the Irish side of the Channel, near "Wexford, almost opposite 

 St. Erth, there is a deposit in many respects similar to the one just 

 referred to. These Wexford shelly sands and gravels contain, as Mr. 

 Bell (5, p. 623) remarks, " a number of forms of Pliocene Age, and 

 otliers of a northern type, the relative proportions suggesting that the 

 northern fauna was gradually superseding the decaying southern one." 

 In the low level drift deposits in the Isle of Man, Mr. Kendall has 

 found (48, p. 17), "besides some Boreal forms, many species charac- 



^ The following species may be quoted as examples : — Strongylocentrotus 

 lividits, Achaeus m-anchii, Inachus leptochims, Gonoplax angxilata^ Thia assidua, 

 Aepophihts Bonnairei, Blennius galerita, and Lepodogaster Decandollii. 



I am indebted to Mr. Nichols for the following additional ones: — Bonaxpolitus 

 •and Amphidesma castaneum. 



