48o DEPTHS OF THE OCEAN chap. 



the tidal area is their proper home. On the other hand, 

 those forms which have been described as passing their 

 hves in the vicinity of low-water mark are not limited to 

 this situation, but may be met with throughout the whole 

 littoral zone, sometimes on sand, sometimes on rock, and 

 sometimes impartially on either hard or soft bottom. Further- 

 more, on the coasts of Norway the majority of the forms which 

 characterise the littoral zone either never, or only to an 

 inconsiderable extent, pass below its lower limit, though there 

 are some that go down to perhaps about lOO metres, and a very 

 few that descend to greater depths. But forms which on the 

 Norwegian west coast are exclusively littoral, may be met 

 with in deeper water in other northern areas, as I shall show 

 later on. 



It would hardly be possible in a short account like this to 

 give even an approximately complete description of the fauna 

 along the coasts in the sublittoral zone, seeing that this is the 

 abode of most coastal species living below the littoral zone. As 

 a rule, the soft bottom is of a different character from that in 

 the deepest parts of the fjords. Instead of viscous gray clay or 

 mud, a coarser clay, more sandy in character, covers the Hoor 

 in the medium depths of the sublittoral zone, which in the case 

 of the fjords is near the sides or on submarine banks. Where 

 there are plateaus sloping gradually down from the sides we 

 also get rocks and stones and bits of shells, and there is thus 

 accommodation for forms that naturally live on hard bottom. 

 We often get, for instance, quantities of brachiopods and 

 bryozoans, as well as a certain number of hydroids, ascidians, 

 etc. Generally speaking, the character of the bottom here is 

 more favourable to animal life than in the deep water, for while 

 the mud harbours chiefly burrowing mussels, for instance, the 

 medium depths accommodate, in addition, a large number of 

 creeping snails, 



A good many forms which occur in the continental deep- 

 sea zone ascend to the sublittoral, and some even as high as 

 the littoral ^ zone. Still for most of them we may put the upper 

 limit of distribution at lOO to 200 metres. Probably, however, 

 their vertical distribution is affected to some extent by the 

 variations in the vertical distribution of the Atlantic water, 

 which may be higher or lower according to the different seasons 



1 For instance, Paguriis ptibcscens, Ophiopholis aculeata, and Terebellides siromi. 



