RAIS 3D CORAL REEFS OF THE RIUKIU CURVE. 5 



while on its eastern coast tlie reefs have been ahnost entirel}' washed 

 away and remain only in detached areas of small extent. The third 

 group was found in a flat piece of land between the largest (A) of the 

 four islands and the one (B) to the west of it ; it also extended to the 

 northern coast of the former. The remaining portions of the coast of 

 Ishigaki-jima are at present covered with a few" remnants of ancient 

 low coral reefs. Generally speaking, the reefs of this island are not 

 thicker than oO or 40 ft. having been built on a wide plateau now raised 

 in some places to an elevation of several hundred feet above the sea. 



The Miyako subgroup consists of the islands of Miyako, Shimoji, 

 Irabu, Kurima, Ikema, Ogami, Tarama and Minna. A very notice- 

 able fact is that all these islands, except one, are built entirely of the 

 raised coral reefs. The island of Miyako, whicli gives the name to the 

 subgroup, is the largest. It is AvhoUy destitute of mountains. The 

 surface is therefore quite flat, with a coast line of about 40 miles. The 

 highest point has an elevation of 378 ft. and is called Xobaragoe, being- 

 situated near Nobara-muni. In the south-eastern part of the island 

 the reefs are thicker than elsewhere and present a perpendicular cliff 

 along the shore, while towards the west they slope down gradually 

 until they pass into the Alluvial plain of the south-western corner of 

 the island. As in other islands terraces are also observable in the reefs 

 of the southern coast westward from Tomori-mura. 



Irabu-jima attains an elevation of 300 ft. in its eastern part, 

 whence it gradually slopes down towards the south-west. Ikema-jima, 

 Tarama-jima, and Minna-jima have elevations of about 100 ft., 105 

 ft., and 15 ft. respectively. In Ögami-jima the reefs are found only 

 on the outer margin of the island. It should here be added that the 

 above mentioned reefs are all horizontal, except in a very limited area 

 in the southern part of Tarama-jima, where they incUne towards the 

 south at an ançrle of 30.° 



