CONTRASTS OF THE CENTRAL AND WESTERN PACIFIC 561 



pelagoes; deeply submerged reefs are less known, but they appear to be 

 well certified in two cases. 



A deeply submerged coral deposit was discovered by the Dutch "Siboga" 

 expedition in the Ceram Sea, west of New Guinea, in 1900, where a 

 dredging brought up large quantities of recent reef -building corals, coated 

 with manganese, from depths of from 1,633 to 1,304 meters, at a d.istance 

 of 42 kilometers from the nearest sealevel reef (Weber, 1903, 80). Mo- 

 lengraaff, who has lately called attention to this extraordinary record, de- 

 scribes the Ceram Sea as occupying "one of the most remarkable trough- 

 shaped deep basins in the eastern part of the Indian archipelago, the 

 origin of which is probably connected with crust movements in Pleisto- 

 cene and post-Pleistocene times. They were formed by downward move- 

 ments, simultaneous with and more or less compensated by elevations of 

 about equal amount of other parts — nowadays highly elevated islands — in 

 that region" (1916, 624). Another case is that of the terraced island of 

 Sumbawa, east of Java, recently described by Elbert. This volcanic 

 island not only bears marks of emerged wave-cut benches up to 1,200 

 meters, and of fringing coral reefs up to 605 meters, but also of sub- 

 merged reef benches at several levels down to a depth of 463 meters. 

 There can be little question that further exploration of the deep basins 

 within the archipelagoes will bring forth facts of extraordinary interest. 



AVERAGE AND INDIVIDUAL VALUES OF LAGOON DEPTHS 



Many other citations might be made in further evidence of the contrast 

 here considered: thus great, long-continued, and slow subsidence of the 

 vast oceanic area is indicated by Pilsbry's researches on the land snails 

 of many mid-Pacific islands, which he has briefly summarized in a recent 

 article (1916), and by Crampton's detailed studies of the land snails of 

 the Society Islands (1916), while the geologically frequent alternations 

 of subsidence and upheavals in the western area are emphasized by Schu- 

 chert, who concludes, on the basis of elaborate geological studies, that 

 "the entire western half of the Pacific bottom, and especially the Australa- 

 sian region, appears to be as mobile as any of the continents of the north- 

 ern hemisphere, with the difference that the sum of the continental move- 

 ments is upwards, while that of the ocean bottom is downwards'^ (1916, 

 105). 



In consideration of all this, it v^ould seem prudent for those who adopt 

 the Glacial-control theory of coral reefs to limit its application, in so far 

 as it assumes long-continued stability of the ocean floor, to the central 

 area of the Pacific Ocean, where most of the islands are atolls, in expla- 

 nation of which the theory seems to have been originally devised, and to 



