MAYOR— THE REEFS OF TUTUILA, SAMOA. 231 



the ancient barrier reef was formed and were thus covered with 

 less than 20 fathoms of water when reefs began again to grow 

 around Tutuila. These reef patches have now approached to within 

 6 or 7 fathoms of the surface in a few places. The average width 

 of the old drowned barrier reef was quite 2,500 feet, and thus, if 

 the growth rate of corals has remained unchanged, it probably ex- 

 isted around the island for a longer time than has sufficed to form 

 the present fringing reefs of Tutuila. The ancient drowned reefs 

 around Tutuila indicate that fringing reefs did not become trans- 

 formed into barrier reefs in the manner postulated in Darwin's 

 Theory but contemporary fringing reefs grew outward and fused 

 with the barriers which were formed in situ along the seaward edges 

 of the submerged platform. 



In formulating his subsidence theory of the supposed sequence 

 of fringing reefs, barrier reefs and atolls, Darwin failed to consider 

 certain factors which are now well recognized. For example, his 

 theory, as he advanced it, presupposes subsidence of the land rather 

 than an elevation of sea level, nor did he consider the effects of 

 cliffing of shores, the making of platforms of marine planation, 

 or the drowning of valleys upon which Davis lays constant emphasis. 

 To his mind coral growth was probably continuous throughout long 

 periods. Just what relations if any existed between periods of gla- 

 ciation and periods of poor development of coral reefs is as yet ob- 

 scure even in the Atlantic. Thus Vaughan ( 1919. U. S. National Mu- 

 seum Bulletin No. 103, p. 226, etc. ; also, igi8,BuU. Geol. Soc. America, 

 Vol. 29, p. 629) shows that in the West Indian-Florida region there 

 was a maximum development of coral reefs in the middle Oligocene, 

 which was a period of maximal submergence in this region, and at 

 which time the Atlantic and Pacific were connected. In the Mio- 

 cene and Pliocene only poor reefs were developed, no Pliocene reefs 

 being known from the West Indian Islands. Later in Pleistocene 

 and recent times there has been an extensive growth of coral reefs. 

 According to Vaughan in the Oligocene fifteen genera of corals 

 found at present only in the Pacific and Indian region were growing 

 in the West Indies. Such genera were Pocillopora, Pavona, Fa- 

 vites, Goniopora, Goniastrea, Galaxca, Stylophora, and Alveopora, 

 and seven others ; but they disappeared from the West Indian reefs 



