238 NATURAL SCIENCE. April, 



manner. I remember an instance near the bank of the river, where a 

 bed of conglomerate was fully exposed, measuring about 30 feet in 

 length, 15 feet in height, and four feet in thickness. In this I found 

 a splendidly preserved incisor of Hippopotanms irravadicus, but not a 

 single other specimen. It must further be mentioned that these 

 conglomerates vary greatly in hardness ; sometimes they are hard and 

 siliceous, ringing under the hammer when struck ; sometimes they are 

 loose masses of concretions of hydroxide of iron, formerly used by the 

 natives for smelting ; sometimes they are soft and earthy ; in fact 

 their physical appearance varies greatly. Some of the smaller beds 

 are exactly like a shingle beach on the sea-shore : more or less rolled 

 clay pebbles, small pieces of wood, and fragments of bone, hardened 

 by a ferruginous solution. Small beds of this kind may extend only 

 for a few feet, but they generally contain an interesting fossil. It was 

 in one of these small layers that I found the polished bone of which I 

 shall presently speak. 



At Yenangyoung the Yenangyoung stage begins with a very 

 conspicuous band of ferruginous conglomerate, which from its per- 

 sistency forms a very good horizon so far as this part of the 

 country is concerned. Its thickness as well as its hardness varies 

 greatly, but the former never exceeds 20 feet. It is followed by soft 

 yellowish sandstone, which at some places immediately above the main 

 bed contains some smaller conglomerate beds. Fossils are, as already 

 stated, frequent but erratic. 



The strata form an anticline, the axis of which runs N.N.W.- 

 S.S.E., dipping at about 30° to 32° towards S.W. and N.E. At the 

 same time the axis drops from a point, which is marked by the oil- 

 field of Twingon (northern part of the Yenangyoung oilfield), in a 

 northern as well as in a southern direction, so that it is quite obvious 

 that the strata form here a kind of dome, the highest point of which 

 would be about 6,000-7,000 feet above sea-level, if there had not been 

 any denudation. It will be seen from this that the line of outcrop 

 of any given bed must form a closed circle, which, in fact, is 

 represented by a rather irregular ellipse, stretched in the direction of 

 the strike. This remarkable structure was first revealed by the 

 careful mapping of the run of the ferruginous conglomerate at the 

 base of the Irrawaddi division. The tilted-up strata were eventually 

 planed down to their present level, forming a low plateau, gently 

 rising from west to east, which has now been cut into by numerous 

 watercourses. 



From the above description of the stratification it is quite clear 

 that a given bed, which dips East and West respectively on each side 

 of the dome, and which does not come up to the surface of the general 

 plateau, may form part of the surface at the northern and southern 

 end of the dome. It is at such a point, where the ferruginous 

 conglomerate, (Zone of Hippothevium antelopinum and Acerothemmi 

 perimense) comes to the surface, although it nowhere else forms part 



