328 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



rate of growth of corals is known to be of such an order of magnitude 

 as to account for the thickness of any known living coral reef by 

 the growth of coral-reef organism since the disappearance of the 

 last great continental glaciers. As Daly is not a specialist on corals, 

 he has made some errors in his discussions of the geologic history 

 and ecology of corals, but these errors do not affect the validity of 

 glacial control being one of the dominant factors in modern coral-reef 

 development. The only important point on which I am not in agree- 

 ment with him is the evaluation of Pleistocene marine planation. I 

 have shown that the Floridian Plateau has existed as a plateau at 

 least since late Eocene time, and there have been extensive submarine 

 flats in certain West Indian areas since late Eocene or Oligocene time. 

 The submarine profiles that I have drawn for the West Indies, 

 Central America, and Australia indicate Pleistocene benching in 

 depths between 26 and 36 fathoms, without deducting anything for 

 Recent upbuilding of the sea bottom. Certain West Indian and 

 Central American reefs and the Australian Great Barrier, I, therefore, 

 believe are growing on what were dry-land areas during at least a 

 part of Pleistocene time. It, therefore, seems to me that many of 

 the flats discussed by Daly are of f re-Pleistocene age, and that he has 

 over-evaluated Pleistocene marine planation. Daly admits that there 

 has been local crustal movement in some coral-reef areas. 



11. Wood Jones is undoubtedly correct in attaching great im- 

 portance to the effects of sediment on the formation of coral reefs. 

 No one who has had actual experience with coral reefs can for a 

 moment doubt it. He also correctly accepts the interpretations 

 of Andrews and of Hedley and Griffith Taylor for the Great Barrier 

 of Australia, joining with the latter two in their opposition to the 

 solution hypothesis and in their emphasis of the effects of wind- 

 induced currents in shaping the segments of a reef. He, however, 

 appears not to have appreciated the importance that, in my opinion, 

 should be attached to submergence as factor in coral-reef formation. 



12. My own opinions can be very simply stated : (a) Fringing reefs 

 seem always to have unconformable basal contacts ; they may be formed 

 after submergence that is not followed by uplift or during intermittent 

 uplift that follows submergence ; that is, they may form during periods 

 of either emergence or submergence of land areas. Are the basal con- 

 tacts really significant ? Must not these contacts in the very nature of 

 the case be unconformable ? If the basement has moved up with 

 reference to sea level and a reef begins along the strand line, the 

 basement of the reef will certainly be different from the reef itself 

 and there will be an obvious unconformity. If the land mass sub- 

 sides and a fringing forms along shore, the base of the reef will surely 

 exhibit unconformable relations. I am unable to imagine a fringing 

 without an unconformable basal contact. I never saw one that did 



