ScHARFF — On the Origin of the European Fauna. 501 



teristic of warmer waters and a notable percentage of extinct species 

 ■of mollusca." It seems probable, therefore, to judge from these de- 

 posits, that, after the St. Erth beds were laid down on the coast of 

 Cornwall, the sea gradually crept up the Irish Channel from the 

 south, and with it the southern fauna ; but that shortly after it had 

 taken possession of the Irish Sea, the advent from another direction 

 of a distinctly northern one, checked all further progress of the 

 southern species, and exterminated a number of them. ISTo one, how- 

 ■ever, has made a more thorough study of the fauna contained in the 

 xecent deposits in the north-east of Ireland than Mr. Praeger, and his 

 Tiews on this subject are tlierefore of value in elucidating the history 

 •of the Irish Sea. In the gravels of Ballyrudder, Co. Antrim, which 

 Tinderlie the boulder- clay, he obtained fifteen species of mollusca of a 

 distinctly Arctic character (70 «, p. 521). In speaking of the boulder- 

 clay of the north-east of Ireland generally, he remarks (70 5, p. 51) : 

 •" Somewhat warmer seas existed during the boulder-clay period, in- 

 ihabited by a fauna still distinctly northern, but containing a few 

 southern forms, along with a diminishing number of Arctic species." 

 "A long period, represented by the Eskers, brick clays, and submerged 

 peat, must have intervened before the depositions of the next bed of 

 the series." " A slight siibmergence allowed the deposition of 

 the Lower estuarine clay with its rather southern fauna." Then 

 followed a further submergence, during which the southern element 

 attained its maximum, and finally came, according to Mr. Praeger, 

 eleviition of land and a distinct return of the fauna towards its 

 northern character. 



Mr. Praeger does not offer any explanation of the causes which 

 have produced these very remarkable changes, which he has traced 

 with such skill through the various dexDosits from the Ballyrudder 

 :gravels underneath the boulder-clay to the most recent surface beds. 



The distinctly southern element in the Ballyrudder fauna is 

 exceedingly small, amounting only to three per cent. It is very unlikely 

 that it came into the district at the same time as the northern. It is 

 much more probable that it must be looked upon as a mere remnant of 

 an older southern fauna, since it has been shown that such a fauna 

 undoubtedly existed in pre-Glacial times in the Atlantic. According 

 to the conclusions I arrived at from a study of the terrestrial fauna of 

 Ireland, this southern element in the Irish sea was admitted by the 

 breaking down of the southern connexion — the connexion between 

 Wicklow and Wales. When the sea with its Arctic fauna invaded 

 Jllngiand from tlie east, and finally joined the Irish Sea, the southern 



