^Ije Itrt^ij Jlrtturalt^t. 



VOLUME XVIII. 



THE BIOLOGICAL vSUBDIVISION OF IRELAND : 



SUPPI.EMKNTARY NOTR. 

 BY JOHN ADAMvS, M. A. 



Whii,e no adverse criticisnivS seem to have been made 

 respecting the twelve-fold division of Ireland which I pro- 

 posed in the Irish Naturalist for August, 1908, in regard to its 

 applicability to the distribution of land and fresh-water species, 

 it has been suggested to me that it is not well adapted for 

 indicating the distribution of marine species, as the boundar}^ 

 line between two adjacent sub-provinces in most cases lies 

 along the middle of a baj-. There is, it must be admitted, 

 much force in this objection. It would certainly' be preferable 

 that any given Bay or Lough should belong to one division 

 only, and in order to meet the views of marine zoologists and 

 botanists, I have attempted to recast slight!}- the divisions of 

 the coast-line, thus getting over the difficulty mentioned. 



Strictly speaking, the area under water is not, I suppose, a 

 part of Ireland, and, in consequence, a certain amount of 

 liberty may be claimed in fixing the boundary between two 

 sub-provinces — provided that it does not deviate too farfrom the 

 actual count}^ limits. At the same time I have tried to preserve 

 the same proportion between the actual length of coast line 

 belonging to each division as existed in the former scheme. 

 It might be as well to add that where a boundar}^ line runs 

 along the shore of a ba}- before turning out to sea, low-water 

 mark is the line which it follows ; in other words, species 

 obtained b}' shore-collecting belong (naturally enough) to the 

 county on whose shores they are collected. 



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