32 ART. 2 -S. YOSHIWARA : 



atKochincla N40°E SE10° 



Ol) tlic road from Kochimk to Hébava NOO°W SW25,° N-S W15,° 



N40°W SW10° 

 nearOyalcawa N40°E SE20° 



The igneous rocks arc îill Fre-tertiary jwrphyrite forming eight 

 dykes, all in the western part of the island. AVith a single exception 

 at Nakama on the east of Onna, where it is X30°W, the strike of the 

 dykes is parallel to the long axis of the island. The fifth dyke, 

 counting from the west, runs exactly along the western coast on the 

 north of the Motobu region. The dykes mostly belong to the mica- 

 porphyrite, and there is no hornblende- porphy rite as in the vicinity of 

 Xaon in Oshinia. All the dykes pierce the Palaeozoic rocks, but never 

 come in contact witli the Tertiary. 



Yagaji-jima is merely a piece of land separated from Okinawa- 

 jima by the action of the sea. The Palaeozoic limestone with compact 

 quartzite is nothing but a continuatiori ofthat in the Motobu region; 

 and the clay slate and sandstone in tlie center of Yagaji-jima are the 

 same as those in the principal part of the larger island. The remain- 

 ing parts are almost wholly occupied by raised coral reefs. Only at 

 the south-eastern corner there is a very small area of Tertiary sand- 

 stone with marl, exposed by the erosion of overlying reefs. This 

 Tertiary rock contains fossil leaves, corals, DentaUum, Tapes, Nassa^ 

 and Trochus. 



Kouri-jima, as well as Sesoko-jima, consists of Palœozoic lime- 

 stone with a belt of raised coral reefs all around it. In the lattei* 

 island, there is Palœozoic sandstone at the north-eastern and south- 

 western ends of the limestone region. Some small exposures of 

 compact quartzite are there found in different places. All these 

 sediments incline to the west or north-west as in the case of the other 

 islands. A dyke of porphy rite is traceable along the eastern side of 



