212 



DALY. 



platform edges, the reefs would there be specially strengthened also 

 because of the extra supply of coral larvae emanating from the suc- 

 cessful colonies. The young corals, as well as the adults, would feel 

 the benefit of a location on the phitform edges. 



The resulting reef must be more or less unsymmetrical. While 

 corals could live on the lagoon side, they would tend to suffer from 

 occasional clouds of sediment washed up from the lagoon floor by 

 major storms. To mud-control one may again appeal as a partial 

 explanation of the more advanced development of atoll reefs on the 

 side of the prevailing wind. 



"Drowned" Atolls and Other Banks. Mud-control may have an 

 important bearing on the abnormal condition of the Great Chagos, 

 Pitt, Macclesfield, Tizard, and some other banks. These are all large, 

 flat platforms, rimmed with dead or living reefs Avhich are covered 

 with 5 to 30 m. of water. Principal data concerning these banks are 

 entered in the following table (IV). 



