498 EIGHTH PACIFIC SCIENCE CONGRESS 



Veretnolpa minuta, Laevicardium undatopicta, Nucula paulula and 

 Microcirce gordonis. 



The similar tendencies of distribution are found in plankton and 

 perhaps in nekton, too. 



The difference of distribution types may be attributed to the dif- 

 ferent degree of influence of the open sea water caused by tide. The 

 tidal ranges differ on the opposite sides of Japan, which reach more 

 than 1 m. on the Pacific Sea side and about 3(>-40 cm. on the Japan Sea 

 side. 



K. Okamura (1926) published an opinion that the poorness of 

 algal flora of the Japan Sea in comparison with that of the Pacific coast 

 was due to the geologically recent origin of the Japan Sea. Although 

 we have not sufficient reasons to deny this theory, the simpler composi- 

 tion of coastal fauna of the Japan Sea may be more reasonably under- 

 stood by simpler ecological conditions including a small tidal range than 

 by historical sequence. 



We have an opinion that more emphasis should be laid in future 

 on the biogeographical study from quantitative and typological view- 

 points than from the taxonomic standpoint. 



Summary 



1) In Japanese bays, there occur the faunal elements of the conti- 

 nental coast, which have much wider distribution ranges than those of 

 the open sea coast and their distribution is little influenced by the 

 oceanic currents. 



2) Some of the continental coastal animals have recently become 

 extinct or remain as relics in some special bays. This fact is proved 

 by the study of shell mounds and it has an important meaning in the 

 segmentation of marine biogeographical micro-provinces around the 

 Japanese Islands. 



3) The bay communities have regionally characteristic distribution 

 types, and we have an opinion that the biogeography based on taxono- 

 mic differences is only one side of biogeography. 



