JOURNAL OF THE COLLEGE OF SCIENCE. IMPERIAL UNIVERSITY 

 TOKYO, JAPAN. 



VOL. XVIII., ARTICLE 6. 



On Some Jurassic Fossils from Rikuzen. 



By 



Matajiro Yokoyama, Rigahihalushi. 



Professor of Palfeontologv, Imperial University of Tokyo. 



With 2 plates. 



About the year 1885, Mr. I. Ban, then geologist to the 

 Imperial Geological Survey, found a Trigonia belonging to the 

 Group of Undulatse at Ho?oura, Eikuzen, a place adjacent to 

 Isadomaye, a well known locality of Pseudomonotis ochotica Keys. 

 of the Upper Triassic. This gave the first hint of the occurrence 

 of Jurassic formation in that part of Japan. 



Subsequently in the years 1887 and 1888, Professor Jimbo 

 made a geological investigation, not only of the district above 

 mentioned, bat also of the adjoining region and fully established 

 the occurrence of Jurassic deposits by the side of the Triassic. 



The present paper is an attempt to determine the age of 

 the respective strata of the Jurassic by data furnished by the study 

 of their fossils, collected partly by Professor Jimbo and partly 

 by Mr. Iki who, in 1895, made a special research in the district 

 around Hosoura. The fossils, although few in number and 

 mostly of ill preservation, are still characteristic enough to give 

 a tolerably clear idea of the geological horizons of the various 

 layers containing them. 



