(GEOLOGIC STRUCTURE OF THE RIUKIÜ CURVE. 27 



especially near the northern part; the western coast is nearly straight, 

 with the exception of the tongue-shaped projections of Motohu, Aka- 

 maruga-saki and Hedo. It is very interesting, that these regions which 

 project out to sea are composed of Palaeozoic sediments entirely differ- 

 ent from those in other places. The highest peak Katsuo-dake, is found 

 in the Motohu region and has an elevation of 1557 ft. ahove the sea- 

 level. The southern part of Okiiiawa-jima is generally plateau-like, 

 and belongs to the Tertiary and Post-tertiary formations. 



The Palteozoic rocks are clay slate, sandstone, pyroxenite or 

 amphibolite, and schalstein found in the main part of the island; and 

 the overlying limestone with compact quartzite, found in the western 

 part, viz. in the regions of Motohu, Akamaruga-saki, Hedo, and in the 

 south of Shioya. In the region of Motolju the dip is variable, but 

 most frequently west or south-west 20 — 70 degrees. PI IV^ shows 

 the kinds of rocks observed in my trip through this region. In the 

 limestone with compact quartzite, belonging to the western part, 

 there are thin layers of slate, sandstone and pyroxenite or amphibolite, 

 all of which are also found in the main part. Moreover the limestone 

 and compact quartzite are conformable with the same rocks in the 

 main part and seem to represent only a later part of the same period 

 as is shown by the dips. In the other islands of the Iliukiu Curve, 

 all of the Palaeozoic rocks are also associated with one another. Thus 

 in Öshima, the two rocks showing generally a westward dip, are 

 found in the western part and are often intercalated in the other 

 Palœozoic rocks, just as in Okinawa-jima. Moreover the islands on the 

 w^est of Okinawa, viz., Sesoko, le and Kouri, and those in the Iheya 

 subo-roup are almost all composed of limestone and compact quartzite 

 and not of other rocks. 



The following'- abstract of my note refers to the P;dci?ozoic rocks 

 lying outside of the Motohu region : 



