RAISED CORAL EEEFS OF THE EIÜKIU CURVE. 



Fii;-. 1. 



T IVrtiary sindstoae. 



K Raised coral reefs. 



from NNE to SSW or from N to S, yet the raised reefs are entirely 

 composed of horizontal beds and form an extensive table-land less than 

 100 ft. in heio-ht (Fig 1). From the facts above stated it is to be 

 inferred that the present island was formerly separated into two by a 

 channel of shallow water, in which the coral polyps built their thick 

 reefs, and that by a subsequent upheaval the two islands were united 

 into a single one. The reefs are at present in two or more terraces 

 near the shore, and their entire thickness is about 30 ft., while the 

 elevation to which they have been upraised attains a height of several 

 hundred feet above the level of the sea. The recent sand on the sea 

 coast of the northern part of the island is nothing but a heap of the 

 «hells of the Foramimfera, Calcarina spengleri Linné. 



Iriomote-jima is composed almost entirely of Tertiary sandstone, 

 the layers of which are more or less regularly inclined, just as in 

 Yonaguni-jima. The highest peak has an elevation of about 1,500 ft., 

 but the raised reefs, only 30 or 40 ft. in thickness and quite horizont- 

 ally bedded, are met with only here and there within a very limited 

 area. In the south-eastern corner called the Haemi region, however, 

 the reefs 20 or 30 ft. in thickness are seen in a continuous sheet on 

 a table-land more than a hundred feet high : this is the case also in 

 Y onaguni-j ima . 



Two small islands, Kayama-jima and Kobama-jima, have only a 



