ECOLOGY OF ROCKY COASTS 329 



one could have an association fragment of Durvillea in the Xipho- 

 phora belt. There is still divergence of opinion about nomenclature, 

 and even at the present time when it is desirable to secure uni- 

 formity, it is still perhaps more satisfactory to use the noncommit- 

 tal term *commimity'. 



So far as the individual belts are concerned our knowledge has 

 now reached the point where some degree of uniformity of nomen- 

 clature is possible. 



The basic zonation of the littoral 



The Stephensons (1949) using their own material and that of 

 other marine ecologists have proposed a basic grouping in the 

 littoral which is now becoming generally accepted. Three major 

 belts are recognized and they appear to be practically universal. 

 These belts are the supra-Httoral fringe, the mid-littoral and the 

 sub (or infra-) Uttoral fringe. The relationsliip of these belts to tide 

 levels and the dominant organisms is shown in the following 

 schema : 



Supra-littoral 



Upper limit littorinids 



Supra-littoral fringe Extreme high water springs 



—Upper limit barnacles 



Mid-littoral 



-Mean low water neaps 



Sub-littoral fringe 



-Upper limit laminarians or certain 

 fucoids 



-Extreme low water springs 



— ? Exact position not settled 



Sub-littoral 



This basic zonation does vary from place to place depending on 

 the inter-relationships of tides and wave action (Fig. 191). 



Some discussion has recently takerv place about the nomencla- 

 ture of these belts, but so many worker:, have accepted the Stephen- 

 son terminology that there seems as yet no v<ilid reason for depart- 

 ing from it. It will be noted that it is based upon limits of living 

 organisms. Japanese workers have suggested that tide levels should 

 be used, but until we know more about the relationship between 



