EAISED COEAL REEFS OF THE RIÜKIU CURVE. '9 



reefs which are found upon this foundation form an extensive table- 

 land in the southern, western and south-eastern parts of the island. 

 Near Ketoku-mura in the north-eastern part of the island, the reefs are 

 scattered in small areas and have a height of only about 50 ft., witli a 

 slight inclination towju'ds the coast. They appear to have been 

 originally built in the valleys of the Palaeozoic mountains. 



Kikai-ga-shima, with a coast line about 20 miles in length, 

 consists of a Tertiary sandy shale, entirely covered with raised coral 

 reefs, which in some places give rise to successive terraces. The shale 

 is exposed only in the western and eastern parts, as at the steep cliff 

 on the south of Sömachi. Here it is covered with a reef from 30 to 

 40 ft. in thickness. The highest part of the clilf lies at Mfibi, and is 

 about 684 ft. above the sea-level. 



Oshima is a large island composed of Palasozoic rocks. The 

 greatest elevation is found on a peak 2,300 ft. in height. The reefs 

 are formed only upon the small tongue-shaped plateau on the north. 

 On its eastern coast the reefs are elevated about 20 or 30 ft., while on 

 the west they have been almost entirely eroded, leaving only on the 

 north-western corner, some relics which are a few feet in thickness. 



II. GENERAL CONSIDERATIOX. 



The coral formation of more remote age, which always stands 

 upon the eroded strata, forms fringing reefs on the islands composed 

 of older rocks, or somtimes separate islands with entirely covered 

 foundations. The latter type is observed at Hateruma-jima, Aragu- 

 suku-jima, Kuro-shima, Miyako-jima, Irabu-jima, Ikema-jima, Shimo- 

 ji-jima, Kurima-jima, Minna-jima, Tarama-jima, Ike-jima and Kudaka- 

 jima. Kikai-ga-shima, Hianja-jima and Miyagusuku-jima are a 

 modification of this type and are reefs with their foundations exposed 

 at the cliffs above the sea- level. 



