20 Art. 1. — M. Yokoyama : 



It will be seen from the above that the species which form the- 

 main mass of the fauna are still living either near the fossil localities 

 (Central Japan) or in the same latitudes more to the west (Western 

 Japan). But among these forms, we have to distinguish those 

 which live exclusively in Central or Western Japan from those 

 which at the same time live either north (in Northern Japan) or 

 south (in Southern Japan) of it. As might be expected, the forms 

 which live exclusively in Central or Western Japan amount to 

 about one-half (114 or about 50%), w^hile those which live at the 

 same time either north or south are much less (74 or 32%). But if 

 we compare the forms which at the same time live north with those 

 which at the same time live south, the former are considerably 

 more in number (45 or 19.4%) than the latter (29 or 12.5%). 

 Moreover, we must note that there are, besides, 14 species which 

 at present are known only from Northern Japan. They are the 

 following : 



1. C%7'ysodomus arthrit'icus Val. 



2. Chrysodoirms schrenchl Yok. 



3. Priene oregoneims Redf. 



4. Punctiirella nobilis Ad. 



5. Panope generosa Gld. 



6. Corbula venusta Gld. 



7. Spisula grayana Sehr. 



8. Solen krusensteriiil Sehr. 



9. T ein fia venulosa Sehr. 



10. Jfacoma nipponica Tok. 



11. Ästarte borealis Chem. 



12. Astarte hakodatensis Yok. 



13. Pectimculus yessoensis Sow. 



14. yucula irmgais Ad. 



And among the foreign forms, there are also two which may 

 be counted among the northern ones- They are Terebratella 

 pulvlnata Gld, of Fuget Sound in Washington and Leda ramsayi 

 Smith'^ of New South Wales, found at a depth of 950 fathoms. It 



1) I was recently told that a form which is either identical with, or close to, this 

 bivalve is found in Northern Japan. 



