KOSSH.S FHOM IHK ICNVlIlÖXö OF TUKYu. 



fl.- 



liroHiiibli thiy 

 Pebble lav<'r 



2^— Bluish day 



Viij:. 5. — Profile showing the boundary line l)et\veen 

 brownish antl bluish clav at Tabata. 



so that these two form a siiiirle heil as is seen on the western 

 side of the Sliinagawa railway cutting and also at Tabata. Next 

 rehiting to this bhiish clay and the overlying brownish one, 

 the ditl'erence of colour is quite unimportant, the line of bound- 

 ai-y between tliem being very irregular at Tabata as shown in 

 the figure -3. The 

 insignificance of tliis 

 line is also shown by 

 a regular horizontal 

 pebbly layer trav- 

 ersed by it. So the 



brown color of clay will be only the result of oxidation caused 

 by the action of percolating water. 



So if indeed any geological gap exists in our profiles, it 

 must be found high up between the brownish clay and the 

 gravel layer and not lower down. Brauns determined the age 

 of our fossil beds to be Pliocene by identifying their moUusks 

 chiefly with those of the Crag. But it very seldom happens 

 that non-pelagic species, either Recent or Pliocene, show so 

 wide a distribution as to be found in Japan and Europe at 

 the same time. No recent Japanese shells, excepting a few, 

 which are mostly cosmopolitan, pass the Red Sea on the one 

 side or the west coast of America on the other. Of the twenty- 

 two species described by Brauns as identical with those of the 

 Crag, only five are so according to mv own determination, and 

 of these four are either cosmopolitan or circumpolar. In 

 Brauns' work no extinct species are mentioned ; but I recogni/e 

 about ten* which are considered as surelv extinct. Still this 



* TrochiiK Khinaf/ait'i'nsis ToK., Tellina serricosltin ToK . TtUina ojienaif ToiC , Cardiiini 

 braunsi Tok;, C'arditu rotunda ToK., Peclcn tokyoenùi Tok., Mysia pncifim TuK., tfrc. 



