ON SOME FOSSILS FROM THE ISLANDS OF FORMOSA & RIU-KIU. 3 



coral-reef formation which enters into the structure of the Rifl- 

 Kiü Islands. A certain modern facies possessed by this material 

 has inclined us to regard it as of Pleistocene age. It is in fact 

 very similar lithologically to some of the reef limestones of 

 Christmas Island (Indian Ocean) winch immediately succeed the 

 Miocene beds of that area and which have been ably described 

 by Dr. Andrews and his co-adjutors in " The Christmas Island 

 Eeport" of 1900. 



A slight variation in colour and lithological character is 

 observed in our specimens of the Riü-Kiü reef-limestones, and 

 they differ sometimes with regard to the prevailing Foraminifera 

 contained in them. Thus the rock from Unten on the west coast 

 of Okinawa is crowded with Operculina complanata and Pulvinu- 

 lina repanda. On the other hand in the rock from Motubu 

 near Unten the Operculina is absent though the Pulvinulina is 

 plentiful. In addition to these organisms, there occurs a modern 

 type of LitJiothamniuin. 



The age of the raised reef-limestones of the Pacific Islands 

 has always been a troublesome problem to the geologist, insuper- 

 able difficulties becoming manifest when he attempts to divide up 

 these deposits into the various horizons of the Tertiary and 

 Quaternary systems. 



Such a result can only be attained by an examination of 

 carefully collected material from the different terraces of eleva- 

 tion, so that each assemblage or colony of organisms would be 

 available for study and comparison. The present samples are by 

 no means sufficient to allow us, with any certainty to make a 

 definite statement on this subject and we prefer, tentatively, to 

 regard our specimens from the BiCi-Km Group as favouring the 

 view that they belong to some part of the Post-Pliocene series. 



