PART 4.] 
Theobald • Beds with fossil wood in Bnrmah. 
85 
must probably be placed the ossiferous beds, at the top of the river reach above Talohmhor 
(Keng-yua in map), yellowish sands pebbly at top and passing up into rather soft conglo¬ 
meratic sandstone containing bones, both mammalian and ohelonian, shark’s teeth and 
vertebr®, fossil-wood and rolled fragments of oysters and other shells. 
A small but instructive section is also seen of these beds in the My on k Naweng, a little 
below Tbarn by agon (Tham-bya-ga-gon), where pale silty shales are seen supporting a great 
thickness of rusty incoherent sand traversed by thin layers of shale and a coarse quartzoso 
conglomerate with clay galls and cavernous hollows incrusted with a layer of the brown 
haunatite, as seen in some sandy beds of the upper division (a). In this conglomerate I .found 
mammalian bones, shark’s teeth, and a small log of fossil-wood about two feet long of very 
similar character, though less completely' mineralized than that found so abundantly in bed a. 
No other fossils were discernible here, nor, as a rule, throughout this division, though towards 
its base, sandstones come in containing marine shells and corals, though neither plentifully 
nor well preserved. These marine beds, however, are naturally more connected witli the 
great group which follows immediately below the present, and which nowhere contains the 
fossil-wood so characteristic of the present group. 
It only' remains to add a few words on the very close restriction to the eastward of 
fossil wood after leaving the area of the fossil-wood group. Nowhere within the area occupied 
by this group is fossil wood, in pieces of the largest dimensions, more liberally distributed 
than along the eastern margin of the deposit along which it is everywhere found abundantly, 
but directly the boundary of the group is passed there is an almost complete absence of 
fossil wood, even in moderate sized pieces. A very close and careful search in some of the 
larger nullas may result in finding a piece here and there for some few miles from the 
houndary, hut that is all, and the question at once presents itself,—has this fossil-wood sand 
extended formerly across the ranges to the eastward and to the Sittang Valley, or was its 
extension in that direction limited by' a boundary somewhat corresponding in its general 
direction with the present boundary of the group ? Without any detailed knowledge of the extent 
of the group on the eastern side of the Pegu rauge, we know the single fact that this 
fossil-wood group occurs in the Sittang Valley, and this and the presumed conformity of it 
with the lower group which constitutes the bulk of the intervening ranges of hills, would 
strongly lead us to regard the group as having once stretched uninterruptedly from the valley 
of the Irawadi across that of the Sittang, or over the entire country bounded to west and 
east, respectively, by the Arakan and Poung Loung chains. That this must have been the 
case with the great hulk of mioeene rocks so largely developed in this part of the Ira wad i Valley 
is certain, but one argument, though a negative one, is, I think, sufficient to make us pause 
before accepting the idea of a continuous extension of the fossil-wood bed over the same 
area as those of the group below it. This argument is the absence which I have alluded to of 
fossil wood for a distance not far short of 50 miles, that is, throughout the entire breadth of 
country occupied by the precipitous hills and tortuous streams of the Pegu range. When we 
reflect on the large size of some of the silicified trunks which may he said to strew the. 
country along the eastern boundary of this group in Eastern Prome, and the abrupt 
cessation of any save the veriest traces thereof, and these hut for a short distance, from the 
boundary, and consider also the imperishable character of much of this fossil wood as 
evinced lyy its abundance in the hard and well worn gravels of the Irawadi Valley, we 
are irresistibly led to question the former extension of this fossil-wood bed across a 
belt of countiy wherein it has left no traces. The evidence is about, as forcible as negative 
evidence can be. Additional weight is also given to it by the fact, that its admission presents 
no difficulties, but quite harmonises with the process which the geological history of 
the district seems to indicate as having occurred. We have only to suppose that the 
deposition of the vast series of mioeene rocks developed in Pegu proceeded uniformly 
(during, possibly, a sy'nehronous elevation, in a gradual manner, of the ocean bed) till 
the entire series, save the topmost members, had been deposited. Lacustrine conditions 
we may now presume to have supervened over portions at- least, of so large an area, and 
the elevation of the Pegu rango of hills commencing about this time would cause the 
first land to appear on a low belt of country occupying in its general arrangement the 
present lino qf the Pegu range. In other words, the deposition of tire uppermost beds 
of the group arid notably' of the fossil-wood sands would lie arrested along a line of country 
not greatly differing from the present boundary of the group. The elevation of the 
Pegu range and its corresponding disturbance of the adjoining strata certainly continued 
