24 Art. 6. — M. Yokoyaina: 



There is also a species among those described as new which is 

 hardly distinguishable from the one now living in the circumpolar 

 seas, and that is Trophon subclavatus. 



From what has been stated above, it can not be doubted that 

 during the deposition of the Lower Musashino the waters near the 

 Miura Peninsula were much colder than they are at the present 

 time, a condition similar to that ascertained by R. Arnold in the 

 Upper Pliocene of California. 



Lastly, if we look at the respective zones into which the 

 whole fauna has been divided, the percentage of the extinct as 

 well as of the boreal forms against the total number of species 

 found in each of them is as follows: 



, T „ r, No. of Spec. No. of Extinct Sp. and No. of Boreal Sp. and 



Name of Zones. Wc { Percentage Percentage. 



Naganuma 86 33 or 38,3% 6 or 6,9% 



Koshiba 74 30 or 40, 5% 13 or 17, 5 ' \ 



Kanazawa 27 8 4 



Kamakura 10 1 3 



Yokosuka 80 20 or 25,0% 3 or 3,7% 



Miyata 96 25 or 26,0% 13 or 13,5% 



Leaving aside the two zones of Kanazawa and Kamakura 

 which have yielded only a small number of fossils, the percentage 

 of the extinct as well as of the boreal forms in the four other zones 

 is subject to a considerable change, a change in which no regularity 

 can be found. But so much is true that the percentage of both 

 forms is greatest in the Koshiba Zone. Therefore, if this is not a 

 chance, I should infer that the cold waters which washed the 

 shores of the Pacific side of Central Japan during the Lower 

 Musashino had its greatest effect on the fauna of the Koshiba 

 Zone, or in other words, the waters were coldest at that time. ( >f 

 course, whether this was true or not, future studies can alone 

 decide. 



1) R. Arnold. Palaeontology and Stratigraphy of the Marine Pliocene and Pleistocene 

 of San Pedro, California (Mem. Calif. Acad. Sei., vol. Ill, 1903) p. 65. 



