CHAPTER VIII 



INVERTEBRATE BOTTOM FAUNA OF THE NORWEGIAN SEA 

 AND NORTH ATLANTIC 



The topography of the Norwegian Sea has been briefly noticed 

 in Chapter IV. and the hydrography in Chapter V. 



The distribution of forms in the Norwegian Sea agrees 

 with the hydrographical conditions, and we can distinguish two 

 great regions, the boreal and the arctic, each of which has its 

 own appropriate fauna. All those parts of the ocean-floor Boreal region 

 covered by Gulf Stream water or by coast-water make up the jlJ^'^w j^n 

 boreal region, while the arctic region is covered by water with Sea. 

 polar characteristics. The temperature and salinity in boreal 

 areas vary greatly in the different water-layers, and are much 

 affected by the seasons. What chiefly distinguishes the boreal 

 region from the arctic region is the higher temperature, which 

 never falls below o C, and over large areas never sinks below 

 6° C. The uppermost water-layer may form an exception, for the 

 temperature may occasionally at the very surface and for a com- 

 paratively short time fall below o' C. High summer temper- 

 atures are characteristic of the upper water-layers, and exercise 

 a considerable effect upon the fauna. The boreal region of the 

 Norwegian Sea includes the North Sea with the Skagerrack and 

 Kattegat, the Norwegian coast plateau as far as the North 

 Cape, the coast plateau of the Faroe Islands, and the south and 

 west coasts of Iceland. 



In the arctic region the temperature and salinity are much Arctic region 

 more uniform than in the boreal region : the temperature is jfor^^gian 

 usually below o° C, though in summer the actual surface may Sea. 

 show higher temperatures under the influence of the sun, but 

 the sun's heat does not penetrate so deeply as in the boreal 

 region ; the salinity varies greatly at the surface, but at the 

 depth of a few metres it is rarely less than -t^o per thousand. 

 The arctic region comprises the coast plateaus of Greenland 



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