NOTE ON THE MICROSCOPIC STRUCTURE OF SOME LIMESTONES FROM CENTRAL BORNEO.
In the same series of rocks with the radiolaria, Prof. Molengraaff met with limestones, sometimes in lenticular beds of inconsiderable thickness, sometimes as nodules and brecciated fragments in sandstones and tuffs. Hand-specimens of these rocks were submitted to me for microscopie examination, more especially with the view of ascertaining if they would afford any information as to the geological age of the rocks, and the following particulars were obtained. The numbers given are those placed on the specimens.
Ser. II. Nos. 244, 264, 274, 285, 480. From a lenticular mass of limestone exposed in the bed of the River Boelit; it is conformably intercalated between diabase and diabase tuffs in the same series as the radiolarian chert and jasper. The rock is light- to brownish-gray, compact and traversed by numerous veins of calcite. It is in part crystalline, in part finely granular. I here are in it a few foraminifera and many fragments of organic structures of uncertain character, also numerous rounded and irregularly shaped grains, apparently pseudo-oolitic, somewhat resembling Girvanella grains, but no characteristic tubes could be recopmized in them.
Ser. II. No. 312. In the bed of the River Boelit; angular fragments of limestone occurring in sandstones with pieces of radiolarian chert (ser. II. No. 311). The limestone fragments are brownish, close-grained, compact, and contain many pseudooolitic grains of the same character as those mentioned above. Under the microscope there are also recognizable; spines of