GEOLOGIC STRUCTURE OF THE RIUKIU CURVE. ^7 



raised reef«. Their Tertiary foundation is exposed only at iShiniajiri 

 on the nortli-eastei-n coast of Miyako-jima, and there the exposure is 

 due to a fault. We lind there a bluish shale conformably overlaid l)y 

 a loose brownish sandstone with a dip SW 15^ or AV 7"^ and a strike 

 N" 20° W or N^-S. I found the rocks to be very rich in fossils, among- 

 which Pecten placunuides Martinf and EancUa elajam lîeck* are pre- 

 dominant. Both are in the Miocene of Java, and the former is also 

 abundant in the Tertiary of Formosa. Xenophora af. dunkerl Martin 

 and Conus aff\ jenhind Martin are also C(jmmon. Besides these, Xatica, 

 Oliva, TurriteUa, Macha, Corhitla, Liitraria, Tapes^ Dosinia, Canlium, 

 Area, Anomia and Ostrca are not rare. Whale bones and crab-claws 

 are also found. A thin black-coloured coal-seam in the strata appears 

 not so late as the fossil wood in the Tertiary of Okinawa-jima. 

 Another thin layer of coal-seam is found in Ogami-jima. 



The Yaeijcuiia Sulxjroup. 



This subgTou[) comprises, besides the two large islands of Jshigaki 

 and Iriomote, ten smaller islands, viz., Yonaguni, Hatoma, Xakanogan, 

 Taketomi, Kayamîi, Kobama, Kami-Kiiro, Shimo-Kuro, Aragusuku 

 and Hateruma. The last four are entirely l)uilt of raised coral reefs. 

 Xakanogan-jima, Hatoma-jima and Yonaguni-jima are composed of 

 Tertiary sediments and niised reefs. Taketomi-jima and Kayama- 

 jima consist of Palœozoic rocks in addition to raised reefs. In the 

 three islands, Ishigaki-jima, Iriomote-jima and Kobama-jima, there are 

 Palœozoic and Tertiary sediments, igneous rocks and raised reefs. 



Ishigaki-jima, showing the most complicated geological structure 

 of any of the islands of the Riukiu Curve, has been visited by ^lessrs. 

 Kada and Kuroiwa and afterwards by myself. We find in this island 



t Martin, Xachträj^e zur Tertiärschichten auf Java. — , S« m?«, dex Geol. lîekhs-MuKeiimx, I 

 Ser., II Band, 1881—83. 



* Martin, Tertiärschichten auf Java, .1880. 



