THE MALAYAN AECHIPELAGO. 103 



three tolerably well-defined étages, yiz., («) the lowest, sandstone, 

 (ß) the middle, marl, and (r) the uppermost, limestone. This 

 complex seems to be developed to full advantage, and at the 

 same time to bo best known,^^^ along the Eiamkiwa river in 

 Tanah-Laut, South Borneo. The first étage affords some technic- 

 ally important coal, and is characterised by the Cyrena bor- 

 7ieensis. The marl étage is rich in fossils and full of Orhitoides 

 and Lithoihamnium. The uppermost bed, the horizon of the 

 limestone contains Orhitoides, Nummtdites, corah, and eclmioids. 

 Basalts and andésites pierce all the beds, but play only an 

 insignificant rôle in rock-formation. 



The Younger Tertiary is also coal-bearing, and has been 

 separately grouped from the Old, not on palœontologic grounds 

 but merely on stratigraphie grounds, and lately, Verbeek"*^^ has 

 recast his former scheme, and now étage « is left to rest in 

 the Eocene, ß is assigned to the Oligocène (Nari group of India), 

 and r to the Younger Miocene ; the Younger Tertiary will thus 

 be Pliocene beds. Diluvial terraces and Alluvial swamps, hold- 

 ing diamond and gold, fill up the drainage basin of Barito, 

 Kapua, Eedjang, Mahakkan, Berau, and Bulongan, thus com- 

 pleting the geology of the island. 



As I have said at the outset, the principal direction of the 

 back-bone and also the prevaling strike of the old beds of the 

 island is north-easterly. The same is true of the detached 

 masses, wherever they occur, with variable dips to north-west 

 and south-east. As the greater part still remains terra incognita, 

 the time has not yet arrived to attempt to unveil the inner 



44) Yerbeek und Bottiger, 'Die Eocänformation von Borneo.' 



45) Neues Jahrbuch für Mineralogie, etc., 1892, I, p. 65. 



