GEOLOGY OP JAPAN 



61 



The formations consist mainly of sandstones and shales with oc- 

 casional intercalations of conglomerates or limestones. Violet or green 

 schalsteins of the Inkstone Series are nsefnl as inkstones in Japan. 

 Fossils found in these formations are : 



In. the Inkstone Series of Nagato ; Hildoceras, Grammoceras, 

 Cocloceras, Dacfylioceras, etc. 

 In the Shizukawa Series ; 



Upper, Cyreva, Ferna, GervilUa, Trigonia, etc. ; 

 Middle, Trigonia, etc. ; 



Lower, Uarpoceras, Sclilotheimia, Lytoceras, etc. 

 In the Tetori Series ; 



Upper, Cyrena, Dosinia, Turritella, etc. ; 

 Middle, Many plant fossils belonging to Polipodiaceae, Peco- 

 pteridae, Teniopteridae, Salviniaceae, Equicetaceae, 

 Zaraieae, Taxaceae and Abietaceae ; 

 Lower, PerispJiinctes, Oppelia, etc. 



(3) Cretaceous System. 



The system is spread very well in South Japan, especially in Kii 

 Peninsula and ShikokTi Island, extending over a wide area on the 

 Pacific board ; while in North Japan it occupies narrow strips of land 

 or small basins, scattered here and there. Jurassic or Triassic strata 

 are often found in the Cretaceous terrain, but as they are hardly 

 distinguishable from those of the Cretaceous, their extent can not be 

 clearly defined. 



The geological age of several Series belonging to this System is 

 shown in the following table : 



