EAISED CORAL REEFS OF THE RIUKIU CURVE. 7. 



upon as mere relics of the once continuous rocks, slowly worn away 

 by denudation (PI II). The eastern half of the district forms a 

 plateau several hundred feet in height. ïow^ards the east it shows a 

 steep escarpment generally with a belt of flat Alluvial plain lying at 

 its base, while towards the west it slopes gently, often exhibiting 

 terraces and ending at the shore in cliifs only a few yards in height. 

 The raised reefs are found not only in Shimajiri, but also in the 

 district of Kunchan, on the east coast near Kin and in the northern 

 part of the tongue-shaped peninsula of Motobu on the west coast, 

 forming in both places a plateau. 



Running parallel to the longitudinal axis of Okinaw^a-jima and 

 near its eastern coast, are six small islands. The base of these islands, 

 except Ike-jima and Kudaka-jima, which are built up entirely oi 

 coral reefs and have an elevation of 30 to 40 ft., is also composed of 

 Tertiary rocks, upon which the raised reefs are placed horizontally just 

 as in Shimajiri. In Hianja-jima the eastern part is the most elevated, 

 and the reefs are here developed to the greatest thickness. 



In Sesoko-jima and Kouri-jima, the center of the island is 

 composed of a Palaeozoic limestone. This limestone is surrounded by a 

 belt of reefs about 1 00 ft. in thickness, which in Sesoko present two 

 or three terraces. le-jima, which is remarkable for having a huge 

 pointed rock rising out of the surrounding hills in the central part of 

 the island, has, for its fundament. Palaeozoic rocks which are however 

 for the most part covered with the coral reefs. The reefs form here as 

 elsewhere an extensive plateau and have a thickness of perhaps 100 ft. 

 or more. The above mentioned pointed rock is a compact Palaeozoic 

 quartzite. Minna-jima is a coral island only a few yards high, while 

 Yagaji-jima has the reefs over only a very small area. The Kerama 

 islands are, so far as I know, entirely destitute of raised reefs. Accord- 

 ing to Mr. T. Kuroiwa, the old coral reefs in Kume-jima and Aguni- 



