INVERTEBRATE BOTTOM FAUNA 487 



and the information received from Iceland and the Faroe 

 Islands is not as yet sufficiently comprehensive to enable one 

 to speak with confidence regarding the composition of the 

 littoral fauna there. In Iceland, however, if we may judge 

 from our knowledge of the hydroid fauna in the boreal coast 

 areas, the conditions are very similar to those on the Scan- 

 dinavian coasts, and the same is true also of the North Sea 

 coasts of Britain. 



If we compare the North Sea coasts with the Skagerrack 

 coasts of Scandinavia we find many points of resemblance, the 

 littoral fauna for the 

 most part living under 

 similar natural con- 

 ditions in both areas. 

 The tides of the 

 Skagerrack, however, 

 are inconsiderable and 

 irregular, and in conse- 

 quence forms, which 

 on the North Sea 

 coasts belong to the 

 low-tide area, can un- 

 doubtedly live here in 

 shallow water and on 

 thesame kind of bottom, 

 but they are not left 

 regularly exposed by 

 the ebb. A good 

 instance of this may be 

 seen in the case of the 

 hydroids Clava squa- 

 mata and Laomedea flexuosa, which are quite common on the 

 fucoids in spite of the fact that the ebb-tide only on rare 

 occasions leaves them exposed. On the other hand, certain 

 species, which are not met with in the low-tide area of the 

 North Sea, and consequently do not patronise the fucus there, 

 attach themselves to these algae on the Skagerrack coasts. It 

 is evident from this that it is not the actual foundation but 

 the natural conditions and the ability to adapt themselves to 

 these conditions which determine the distribution of the animals 

 in the strand-belt. 



Although the littoral faunas of these two coastal areas bear 

 a very strong resemblance to each other, there are yet 



Fig. 345. 

 Gorgonoccplialiis linckii, M. and T. 



^'ar. Reduced. 



