AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 39 
rine erosion from the former extension of the slopes of the rim or of its 
spurs. These have been more or less connected together by the subse- 
quent growth of the corals which have found a footing upon them. 
Kini Kini and the other islets about Totoya, as well as the negro-heads 
on the reef flats and patches, all show the volcanic substructure upon 
which has grown and is thriving now a thin crust of corals. 
TOTOYA FROM THE NORTHEAST, DISTANT FIVE MILES. 
It has been difficult to explain the great depth in some of the lagoons 
of some atolls (60 fathoms). It seems to me that the conditions occur- 
ring in an island like Totoya give us a simple explanation of what such 
depths mean in coral districts situated in volcanic regions. Provided 
that we assume that these lagoons are in a region of elevation, as are the 
Fiji Islands, and that its volcanic peaks or ridges and volcanoes have 
been denuded and eroded, and that nothing has been left to indicate 
their former existence beyond the reef flats upon which the corals of the 
present day are growing. Remembering also that the corals can form 
but an insignificant crust upon the slopes and flats which have been pre- 
pared for their growth by the processes of elevation and of subsequent 
erosion and denudation, and that the features characteristic of the 
existing state of things was not brought about by the growth of the 
coral reefs of to-day except in a very secondary manner. We are not 
discussing the question of the formation of great limestone banks by 
subsidence to attain the proper depth at which corals may begin to grow. 
We are only trying to give an explanation of the conditions which must 
have preceded and have led to the existing state of things. 
The deepest water in the crater basin of Totoya is thirty-five fathoms, 
and it certainly cannot be held that a lagoon of such a depth has been 
formed by subsidence after the coral reefs have begun to grow. Let 
us now follow what would have become of Totoya had the denudation 
and submarine erosion which have brought it to its present state been 
continued during alonger period of time. A very few fathoms more, and 
we should have the rim divided into three large islands,—an eastern 
