222 



OUTLIERS. 



with the rest of Spain and the Bay of Biscay. In 

 like manner it is not supposed that the southern 

 forms of the south-west of Ireland have migrated 

 there from the south, across the deep waters of the 

 opening of the channel, but that their presence 

 there, so far as present influences are concerned, 

 is dependent on the peculiar local conditions of 

 that coast as to temperature. 



These considerations lead to the inquiry as to 

 the meaning of those local assemblages which have 

 been observed in several parts of our Celtic pro- 

 vince, the existence of which was first detected by 

 Ed. Forbes, and for which he proposed the name of 

 u outliers." 



" At certain spots we find assemblages of north- 

 ern forms, so peculiar and so isolated, that we can- 

 not account for them by any facts connected with 

 the present disposition of currents, or other trans- 

 porting influence." These patches are especially to 

 be met with in the Clyde district, and among the 

 Hebrides ; on the east coast in the Murray Frith. 

 It is probable there is another patch somewhere 

 near the Nymph Bank, on the S.E. coast of Ire- 

 land, and another in the German Ocean. 



These " outliers " are usually located in a hole 

 or valley of considerable depth, from eighty to be- 

 yond 100 fathoms, and consist of assemblages of 

 Mollusks, of more northern character than the 

 zone or province in which they occur. The species 

 which Ed. Forbes cites, are Cemoria Noachina, 



