488 



DEPTHS OF THE OCEAN 



some differences between them. Thus several forms that 

 abound on the west coast of Norway are absent from the 

 Skagerrack coast, if we may judge from my observations at 

 Risor in Norway compared with the researches of Theel at 

 Kristineberg in Bohuslan.^ For instance, Cuctunaria froiidosa, 

 a littoral echinoderm common on the North Sea coast, has 

 not been met with in the Skagerrack, and Ophiocoma nigj^a is 

 very rarely found in the latter area. Echiims acutiis occurs in 

 enormous quantities on the North Sea coast, but is extremely 



Fig. 346. 

 Psoitis squamatus, Koren. 



rare on the Skagerrack coast, while the mussel, Lima kians, 

 has not been met with on the Bohuslan coast of Sweden, 

 though in certain localities of the Norwegian west coast it is 

 one of the most characteristic forms of the littoral fauna. On 

 the other hand, the Skagerrack coast is the home of certain 

 littoral forms which occur but rarely on the coast of the North 

 Sea. Thus on the west coast of Norway Echmocardium 

 cor datum is seldom found, and then only in a few special 

 localities, whereas in Bohuslan it seems to be one of the 



^ Theel, " Om utvecklingen af Sveriges zoologiska hafsstation Kristineberg och om djurlifvet 

 i angrjinsande haf och fjordar," Arkiv. f. Zoologie, Bd. iv., 1907. 



