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At the former eastern coast of Sunda Land the relations are much 
clearer and less disputable. Here the stable Sunda Land borders on 
the unstable area of the sea of the Moluccas, more especially on the 
Strait of Macassar, one of the many deep-sea troughs that are still 
getting deeper and deeper, while other parts, the present islands, 
are still rising. In the pleistocene age this area between Borneo and 
Celebes was subsiding, and consequently the conditions for the 
development of a shelf on the east coast of Sunda Land at that 
time were unfavourable. The subsiding sea-floor brought the sedi- 
ments, supplied by Sunda Land, down to such deep levels that 
shelf-formation was out of the question. The Sunda Land was thus 
bounded on the east by a deep sea, the present Macassar Strait, and 
its coast must have been steep on that side. There was no shelf. 
Thus ideal conditions for the growth of corals were realized: a deep 
sea, decidedly with clear and salt water, a strong surf, and a fairly 
steep, partly rocky shore. No. wonder that along this coast a fringing- 
reef flourished well. 
And what can be seen now? 
On the most northern margin of the Sunda-shelf, the so-called 
Borneo Bank, stands a reef (Fig 3) rising as a narrow wall, inter- 
rupted in many places, from a depth of 70 to 90 m. to the 
surface of the sea, or nearly so. From this reef towards the land 
the depth of the sea decreases only very slowly from 70 m. down- 
ward; towards the sea, the Strait of Macassar, the depth increases very 
rapidly, in some places precipitously to 200 m. and more. A 
depth of about 1000 m. is found at a distance of some kilometers 
from this reef. This reef stands on the margin of the pleistocene 
Sunda Land; in pleistocene time, before the melting of the ice-caps 
in high latitudes, it was a fringing-reef attached to its shore and 
gradually as the Sunda-peneplain was being submerged by the sea, 
the corals were building the reef up. Nowadays it is a true barrier- 
reef, grown up round the disappearing Sunda Land in the manner 
as DARWIN supposes barrier-reefs to have developed generally. 
Only this reef does not at first sight make the impression of a 
barrier-reef, because the land to which it belongs, has been flooded, 
in relation to the depth of the water, to such an exceptionally great 
distance. On close examination of the course of this reef, which may 
be termed the Great Sunda barrier-reef, it appears to begin at the 
Ambungi-reef, which belongs to the “Kleine Paternoster-eilanden’’. 
This small group of coral-islands, extending in east-westerly direction 
from Tandjong Aru to about 75 km. from the coast of Borneo, is 
perhaps to be considered as the most northern limit of the Sunda- 
