REVIEWS 
Het Verband tusschen den plistoceenen Ijstujd en het Ontstaan der 
Soenda-Zee (Java- en Zuid-Chineesche Zee) en de Invloed daarvan 
op de Verspreiding der Koraalriffen. ... . (The Sunda Sea and 
Its Barrier Reef.) Door G. A. F. MoLencrAAre) 2 
K. Akad. Wet. Amsterdam, Verslag der Afdeeling Natuurk., 
Vol. XXVIII, 1919, pp. 497-533- 
The shallow Java Sea between Java-Sumatra and Borneo and the 
confluent shallow southern part of the China Sea are united by Molen- 
graaff under a single name, the Sunda Sea. He accounts for the flat 
sea floor, nowhere more than 40 fathoms deep, by supposing that, so far 
as its area was already a lowland of weak rocks in pre-Glacial time, it 
was worn down still lower during the Glacial epochs of lowered sea 
surface, and that its deeper, sea-covered parts were in the same epochs 
filled up to a corresponding level. Large rivers, fed by the heavy rainfall 
of the region, are thought to have been active agents of gradation. 
The degraded and aggraded lowland was submerged and the present 
sea created when the ocean finally rose to its normal level in post-Glacial 
time. The margin of the submerged lowland is assumed to lie at the 
present 40-fathom line, outside of which a relatively rapid descent is 
made to deep water. Evidence of submergence is found not only in the 
embayed mouths of tributary rivers not yet filled with deltas, but also 
in the occurrence of detrital tin ore in the extension of river courses a 
mile or more from the shore of certain tin-bearing islands. The fine 
sediments by which the sea bottom is now covered are regarded as river 
deposits laid down while the sea was rising to its present level. 
Although the’ region here considered—Sundaland, as Molengraaff 
calls it—is known on the basis of abundant geological evidence to have 
long been much more stable than the disturbed region of the several 
deep seas and many islands farther east, the essential exclusion of 
crustal subsidence and the restriction of the Sunda sea-floor origin to so 
short a geological interval as the Glacial epochs of the Glacial period 
seem open to question. Moreover, the present margin of the shallow 
floor near the 40-fathom line, which Molengraaff regards as the built-out 
border of the worn-down lowland when the Glacial ocean was lowered, 
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