182 A.IÎT. 2. — B. KOTO: 



If I am justified in my opinion, the Korean Jura 

 is bnt imperfectly represented in its lower horizons. 

 The other side of the Strait of Tsnshima passed that 

 time in a continental, erosion period, while this side 

 was under the sea, harboring the Ammonite fanna. 



I have here purposely inserted the above few 

 lines in order to call the attention of readers to the 

 similar and dissimilar aspects of the Mesozoic devel- 

 opment, especially of the Jurassic, on the two sides 

 of the strait. 

 From what has been said before, one cannot help thinking 

 that the Mesozoic beds on both sides of the Strait of Tsushima 

 are lithologically one and the same formation — the sandstone 

 and marl in the lower, the red tuff- marl and green eruptives in 

 the higher horizon, if we set aside the consideration of fossils. 

 The Korean Jura is mainly represented by brackish water 

 deposits of the Malm-Dogger age ; while our Jura, by the Liassic 

 marine deposits. 



If any one journeys over the Kyöng-sang province and the 

 environs of Shimonoseki, he is sure to receive the impression 

 that he is meeting with the same succession of strata and the 

 same kinds of rocks. 



If we approach the question from the geographical point 

 of view, interesting light will be shed on the Mesozoic on both 

 sides of the Strait of Tsushima as well as of the intervening 

 space, which for brevity will be hereafter called the " Tsushima 

 basin." The Mesozoic belt on the Japanese side trends from 

 northeast to southwest, and that of the Korean also in the same 

 direction. If we outline the supposed extent of the " Tsushima 

 basin " area, a wide belt of the Mesozoic terrane will embrace 



