216 Dr. H. Yabe — Neiv Pleistocene Fauna from Tokyo. 



Shinagawa with the Oji fauna and the estuarine shell and plant beds 

 of Tabata. This proposal is made parti y for the purpose of avoiding 

 the undesirable method of employing such vague terms as Pliocene or 

 Pleistocene for the beds of Oji, etc. There is no doubt that Professor 

 Brauns was mistaken in claiming the Oji fauna to be of Pliocene age, 

 as also was Mr. Suzuki for the estuarine bed ; on the other hand, the 

 statement of Mr. Tokunaga favouring the Diluvial age of the Tokyo 

 Series is in part quite correct. 1 Mr. Tokunaga had determined ten 

 extinct species and 155 species belonging to modern forms ; the 

 percentage of extinct species to the living is too small to assume the 

 series to be of Pliocene age. It is, however, not quite clear how far 

 the application of the European standard of ratio between the living 

 and extinct molluscan species can be relied upon for the correlation 

 of the geological age of a certain late Caiuozoic formation in Japan, 

 especially in so widely distant a part of the world. 



The Diluvial age of the series now under consideration appears to 

 be further supported by additional evidence, afforded by the presence 

 of molar teeth of Elephas antiquus, Falc, which it seems have been 

 obtained from the estuarine clay-bed of Tabata. It must also be 

 taken into consideration that the Kendang or Trinil Beds of Trinil, 

 Java, with abundant mammalian remains, are still under dispute as to 

 their geological position ; the question being whether the complex is 

 of Pliocene or Pleistocene age. In the present case more uncertainty 

 exists because it is somewhat doubtful whether the molar teeth were 

 found in the topmost bed of the Tokyo Series or whether they were 

 obtained from the overlying sand-bed of the Narita Series. 



But practically it is insignificant whether the Tokyo Series is of 

 Pliocence or Pleistocene age, the constitution and general facies of 

 the fauna being now fully known to us by the detailed study 

 of Mr. Tokunaga ; one of his conclusions, however, must be con- 

 sidered with great caution, viz. that the sea near Tokyo was inhabited 

 at that time by molluscs of a climate colder than that which now 

 prevails. This generalization is quite untenable, but it is possible 

 that the relative influence of the cold and warm currents alone, 

 which have followed nearly the same course since Jurassic times, 

 when the Behring Strait was opened or any other similar water 

 communication existed between the Polar seas and the North Pacific 

 Ocean, and without any other essential climatic change in reality 

 may have produced the same effect on the marine organisms living 

 in a shallow inlet of the sea as once existed in the region where 

 Tokyo now stands. 



Such unconformity in deposition is not unfrequent in estuarine and 

 strand formations, and must not be taken as an indication of an 

 important stratigraphical gap between two successive formations. 

 Professor Brauns also paid early attention to the existence of such 

 unconformity in our diluvial deposits and explained likewise its 

 stratigraphical insignificance ; he was only misled by the wavy 

 surface of the shell-bed of Oji and Shinagawa, which he took as 



1 He enumerated Diplodonta pacifica among the extinct species ; but it is 

 found living in the surrounding seas of Hokkaido and also, though more 

 seldom, along the east coast of Honshyu (main island of Japan). 



