﻿312 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



The condition of the reef between Taunoa Pass and Point Venus 

 is interesting in this connection. Alexander Agassiz has given a 

 good description of this part of the reef and reef platform and has 

 reproduced the British Admiralty chart of it.^ Agassiz says: 



Reef patches, the remnants of a former barrier reef, extend westward from Venus 

 Point parallel with the shore of Matavai Bay, forming the chain of Toa Tea reefs, but 

 they are merely patches of Nullipores, with here and there diminutive coral heads 

 which have taken no part in the building of theee reefs. 



There is along the Toa Tea Reefs a great break in the continuity of 

 the reef, but the platform continues, irrespective of the presence or 

 absence of a margining barrier. The depths in Matavai Bay, 16 to 17 

 fathoms, seem to be the maximum, are about the same as in Papiete 

 Harbor, outside which there is a well-developed reef crossed by 

 Papiete Pass. These reefs, also, seem to me to have grown up dis- 

 connectedly on a submerged coastal flat. 



SMALLER ISLANDS OF THE SOCIETY GROUP. 



Alexander Agassiz has described each of these islands in his coral 

 reefs of the Tropical Pacific,^ and P. Marshall has made the observa- 

 tions and deductions recorded in the following quotation:^ 



This reef marks the edge of the platform of marine erosion as described by Agassiz, 

 but the original margin of the land before depression as described by Darwin and 

 Dana. * * * 



It is evident that if the coral reef rises on the edge of a platform of marine erosion 

 this very erosion would have worn the spurs back in such a way that they would 

 terminate in steep cliffs. In no instance at Huaheine, Raiatea, or Tahiti that the 

 author observed, did the spurs have an abrupt termination. The lower slopes of the 

 islands are in all cases notably less steep than the upper slopes. 



The deep inlets that intersect the coast line of Huaheine, Tahaa, and Raiatea are 

 clearly due to stream erosion. Prolonged marine action would have shallowed or 

 filled them up or at least would have built up bars of coastal debris across the entrances. 



The author is therefore strongly of opinion that the absence of cliffs at the termina- 

 tion of radiating spurs, the presence of deep water in the lagoon, and of far-reaching 

 inlets, prove that marine erosion has not had any influence on the form of these islands 

 at the present sea level. * * * 



Finally the deep inlets appear to be drowned stream valleys and their nature 

 strongly supports the belief that they have been subjected to an important movement 

 of subsidence. 



Mehetia is interesting in that it is a young volcanic island, with a 

 strongly cliffed shore, a very narrow or no platform, and no coral 

 reefs around it, only a few coral patches. That the other islands, 

 Murea, Huaheine, Raiatea, Tahaa, Bora-Bora, and Maupiti have 

 undergone geologically Recent submergence and that the barrier reefs 

 have developed during or after submergence, can not be controverted. 

 Is the reef flat due to marine planation and to terrigenous sediments 



1 Agassiz, Alexander, The coral reefs of the Tropical Pacific, Mus. Comp. Zool. Mem., vol. 28, pp. 152- 

 154, pi. 209, 1903. 



2 Idem, pp. 140, 141, 156-167. 



3 Marshall, P., Oceania, Handb. regionalen Geologie, vol. 7, Abt. 2, p. 13, 1912. 



