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XXVIII. 



A LIST OF THE MAEIXE MOLLUSCA OF IRELAND. Br 

 A. R. mCHOLS, B.A. (BEPOBT FEOM THE FAUNA 

 AND FLORA COMMITTEE.) 



[Eead May 8, 1899.] 



MoEE than forty years have elapsed since the puhlication of the fourth 

 Tolume of Thompson's "Natural History of Ireland," which contained 

 an account of the distrihution of the marine MoUusca of Ireland as 

 then known. During this interval the Deep Sea Dredging Expeditions 

 of the "Porcupine," 1869, Royal Irish Academy, 1885, 1886, 1888, 

 &c., have considerahly extended our knowledge of the MoUuscan 

 Fauna of the deep water off the western coasts of Ireland. Dredgings 

 have also taken place off the N.E. coast, and shore collectings have 

 been made at various places round the coast. 



The marine area of Ireland may he divided into two portions, a 

 shallow water district whose depth ranges fi'om to 100 fathoms, 

 and a deep water district with a depth ranging from 100 to 1000 

 fathoms. The boundaries of this shallow water district are the 56° 

 parallel of latitude on the north, a line half-way between Scotland, 

 Wales, and England on the east, the 49° 30' parallel of latitude on 

 the south, and the 100 fathoms line on the west: The deep water 

 district is practically confined to the western coast, and comprises the 

 area contained between the 100 fathoms line and the 1000 fathoms 

 line, and the parallels of latitude 56° and 49° 30'. Canon Norman 

 has suggested the 1500 fathoms line as the limit of the deep water 

 marine area of the British Isles, because it forms a more natural 

 boundary; but off the N."W. coast of Ireland the 1500 fathoms line 

 does not appear to be reached for nearly 1000 miles. The 1000 

 fathoms line gives a more convenient and circumscribed area, and I 

 have therefore adopted it in this list. If the 1500 fathoms line had 

 been chosen, the only difference would have been the addition of 12 

 deep water species. 



For the convenience of denoting the distribution of the species 

 round the coast of Ireland, I have divided it into six provinces, 



E.I.A. PHOC, SEE. m., VOL. V. 2 M 



