Reviews — Mining in the Butch East Indies. 179 



these clues, the author falls back on similarity in lithological 

 -characters and the degree of disturbance as evidence of correlation. 



The oldest sedimentary rocks in West Borneo are dark, hard 

 lustrous clay-slates of considerable thickness, without any admixture 

 of either sandstones or limestones. No fossils have as yet been met 

 with in them. The beds are strongly folded. With the exception 

 of the higher beds of the series, which are supposed to be of Lower 

 Triassic age, these slates are regarded as Palseozoic. They probably 

 correspond to the ' Old Slate Formation ' of Molengraaff. 



Next above the clay-slates, the rocks consist of micaceous shales 

 and pyritous sandstones, frequently alternating. Associated with 

 the sediments there are massive beds of quartz-porphyry and diabase. 

 In one locality an undoubted Triassic fossil, Mbnotis salinaria, is 

 present, and serves to mark the age of these rocks ; also, in siliceous 

 marls and in beds of tuff, Eadiolaria occur. 



Succeeding the Triassic there comes a series of deposits of shales, 

 marls, sandstones, and occasionally limestones, frequently fossil iferous, 

 belonging to the Jurassic period. The Lias is shown in one locality 

 by the occurrence of Harpoceras radians ; casts of Perisphinctes may 

 indicate Middle or Upper Jura, whilst on higher horizons of the age 

 of the Dogger there are shales and marls containing Exelissa, 

 Corhula, Astarte, and Protocarclium, in places sufficiently numerous 

 to form a shell-breccia. 



Nearly at the base of the Jurassic series, in the neighbourhood 

 of Kendai, there are beds of siliceous shales and marls with a total 

 thickness of about 450 metres, which are rich in Radiolaria, but 

 with the exception of a cast of Corhula other fossils were not met 

 with in them. Most of the commoner forms of the Radiolaria 

 described by Hinde in Molengraaff's work were recognized by the 

 author in these deposits, and he is enabled thereby to confirm 

 the opinion expressed by Hinde that they are Jurassic in age. 

 Mr. Wing Easton, however, calls in question the accuracy of 

 Molengraaff's view of the oceanic character of these radiolarian rocks, 

 and considers that they are of brackish-water origin, mainly, it 

 would appear, on the ground that higher in the series they are 

 overlain by thick beds of hard sandstones containing Corhula and 

 other shells indicating shallow-water conditions. 



Deposits of fine sandstones, tuffs, shales, and marls with Radiolaria, 

 and accompanied by thick beds of diabase and propylite, are referred 

 to the Lower and Middle Cretaceous. Fossils are rare and limited 

 to one locality. Species of the Ammonite genus Knemoceras have 

 been determined by Dr. Krause, and are regarded as Cenomanian in 

 age ; whilst two Gasteropods, Itiera scalaris, Vogel, and Nerinea sp., 

 may be of Gault age. 



Sedimentary deposits of Tertiary age have not been met with in 

 this part of Borneo, but this period is represented by eruptive rocks, 

 mainly of hornblende-andesite, hypersthene-andesite, and basalt ; 

 this last forms extensive surface beds and gigantic flows. 



The mineral wealth of Western Borneo has been greatly over- 

 estimated : neither coal nor petroleum has been found ; cinnabar, 



