2 28 JORDAN: ON THE GENUS FUSUS. 



found around the Shetland Isles also occur off the coasts of 

 Portugal and Africa. 



Moreover some species of mollusca accommodate them- 

 selves to a great range of temperature ; for example, Fusus 

 islandicus lives in water of arctic frigidity (30"o° Fahr.) in the 

 Faroe Channel and is found living at the entrance of the 

 Bristol Channel in 40 — 50 fathoms, where the bottom tempera- 

 ture probably is 51 "0° or 52*0° Fahr., a difference of 22"o°. The 

 same fact applies to Fusus Bernicie?isis which lives in the Faroe 

 Channel in 640 fathoms, with a bottom temperature of 30*0° 

 Fahr., and in the Bay of Biscay, or rather in the 'Slopes of the 

 Channel,' with a bottom temperature of 50 0° Fahr. 



The facts above stated lead me to the conclusion that the 

 limit suggested many years ago, namely, an imaginary line drawn 

 equidistant from the British Isles and the territories of other 

 states, is — after all — open to less objection than any other, 

 although it involves going half-way across the Atlantic. 



I am aware that the late Dr. Gwyn Jeffreys stated that such 

 a limit is neither ' rational nor national,' although at one time it 

 had his support, but with great respect I submit that it is as 

 ' rational ' and ' national ' as any other. Moreover those 

 Naturalists who, like Dr. Jeffreys, advocate a ' North Atlantic ' 

 or ' Oceanic ' area will experience just as great a difficulty in 

 defining their limits. 



Shall the ' North Atlantic ' area include the English and 

 Bristol Channels, the Irish and North Seas, and the Faroe 

 Channel ? If not, why not ? If it does, how near to our coast 

 lines shall it approach ? 



No doubt a line must be drawn somewhere, and as Dr. 

 Murray says " We must, if we wish a limit, fix an artificial one." 



I venture to suggest that the widest limit should be adopted 

 — so as to include as rich a fauna as possible — provided that 

 that limit is as rational as any other. Adopting this view several 

 species will be included in this paper which hitherto have not 

 appeared in our British lists. Those Naturalists who do not 



J.C., vi., July, 1S90, 



