An Outline of the Tertiary Geology of Burma. 488 



Sliau Plateau on the east and by the great fold-range of the Arakan 

 Yoma on the west. Whilst the boundary is sharply defined on 

 the east, on the west the Tertiary region rises somewhat gi-adually 

 from the Irrawaddv Valley to the foot-hills of the Arakans. It is by 



Fig. 1. — The Natural Eegions of Burma. 

 L. D. S. 



Fig. 



-Tbe Geography of Early Tertiary 

 Times.— L. D. S. 



no means a monotonous tract. Its southern half is occupied by 

 the valleys of the Irrawaddy and Sittang rivers on the west and 

 east respectively, separated by the low, but somewhat inaccessible 

 range of the Pegu Yoma. In the south one may distinguish as a 

 separate region the great flat delta of the Irrawaddy, dropping very 



