64 ART. 2— s. YOSHIWARA: 



regular inclination, and are limited to definite zones. The raised reefs, 

 which are found in various districts, are however quite horizontal. 

 Only the Tertiary rocks in the northern half are rather irregularly 

 inclined, sometimes being horizontal. The principal rocks of the 

 Curve are the Palœozoic, in which limestone and compact quartzite 

 show the occurrence different from slate, sandstone, and pyroxenite or 

 amphibolite. The latter series of rocks are found in a zone running 

 through Osliima, Tokuno-shima, Okinoerabu-jima Yoron-jima, Oki- 

 nawa-jima, the Kerama subgroup, Ishigaki-jima and Iriomote-jima. 

 'l.'he former are found on the western side, namely in the western part 

 of Oshima, the Iheya subgroup, the tongue-shaped western region of 

 Okinawa-jima, in its dependent isles, le, Sesoko, Yagaji and Kouri, 

 besides in Ishigaki-jima and Taketomi-jima. l^oth series are all 

 regularly inclined. Thus in Oshima and Okinawa-jima, they have the 

 strike parallel to the length of the island and the dip toward the west. 

 Ill Tokuno-shima, Okinoerabu-jima and others, we find either the same 

 strike of rocks or the longer axis of the island parallel to the Riukiu 

 Curve. T'he islands of the Iheya subgroup are arranged parallel to 

 the Curve. Though the rocks in the Yaeyama subgroup have been 

 partly disturbed by volcanic eruptions, yet they show on the whole 

 regular dips. A continuation of the above mentioned Palœozoic rocks 

 is also found in Formosa, in the interior of which slate prevails and 

 otlicr rcjrks are of limited occurrence. The above-mentioned systems 

 of rocks belong to the so-called median roir of islands in the Riukiu 

 Curve. 



r]ru])ted through tliese rocks, there are various Pre-tertiary 

 igneous rocks, the chief of which are granite and diorite, found in 

 \ aku-shinia, Oshima, Tokuno-shima, Ishigaki-jima and Hoa-pin-su. 

 Similar granite is found near Giraii in Formosa, and in the south- 

 eastern part of Kyushu. 



