10 E. C. ANDREWS. 
A CONTRIBUTION TO THE HYPOTHESIS OF CORAL REEF 
FORMATIONS. 
Previous Work. | 
The literature on coral reefs is voluminous, as considered 
from the time of Darwin to the present day. Vaughan’ 
divides hypotheses of coral formations into three main 
groups. 
1. Darwin-Dana Hypothesis [Supported by David (Funa- 
futi) and Davis]. 
According to these authors corals first form a fringing 
reef along the shore of a subsided land area, the reef grow- 
ing upward at arate such that its upper portion remains 
near the surface of the water. By continued submergence 
the shore reef is converted into a barrier. Continued sub- 
sidence where the enclosing land area is an island may 
result in the production of an atoll. 
2. Semper-Murray Hypothesis. 
These authors considered that atolls could be formed in 
Stable areas, or even those of elevation, by the solution of 
the limestone masses forming coral reefs and that currents 
and waves “‘can develop channels behind fringing reefs, 
and in that way transform a fringing reef into a barrier.”’ 
3. The Third hypothesis, as shown by Vaughan, has grown 
gradually from the work of many observers whose main 
ideas fall naturally into two types, namely, those who. 
believe that “‘off-shore reefs have formed on antecedent 
flattish basements or platforms during or after submergence 
in areas where ecologic conditions are favourable for the 
life of reef-bearing corals,”’ 
continental shelves, as also island shelves, have been 
formed by marine action during the great ice visitation of 
the Pleistocene Period, and that coral reefs have thriven 

1 T. Wayland Vaughan. Coral and the Formation of Coral Reefs, 
Annual Report Smithsonian Inst., 1917, p. 189. 
and those who consider that. 
