38 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
northeastern extremity ; it follows irregularly the outline of the shore at 
a distance varying from one to over two miles. The outer reef off the 
north coast is broken into distant patches, leaving broad passages between 
them. North of the western passage the reef is also interrupted, leaving 
a boat passage. The outer reef flats are irregularly trapezoidal in out- 
line, and quite narrow. The greatest depth in the outer lagoon is 27 
fathoms. The eastern arm, and also the northern horn of the lagoon 
and the inner edge of the southern face of the outer reef, are studded 
with rocks and coral patches. The corals on the reef flats are thriving, 
and those on the patches inside of the lagoon are everywhere most flour- 
ishing. Many of the patches close to the outer shore line are in the 
extension of lateral spurs which have been eroded from the ridge of the 
rim. The general depth of the outer lagoon is over 20 fathoms along 
its central channel. Similar spurs run into the inner basin, and have 
formed extensive spits on which corals flourish, or islets and islands such 
as those figured on Plate 69, near the inner edge of the northern rim of 
Totoya. Near the centre of the basin there is an extensive coral patch, 
Kini Kini (Plate 23), formed upon the sides of a small islet rising from 
the bottom of the crater, as is so often the case in the craters of other 
volcanoes (see Plate 71). The volcanic rocks forming its centre are 
exposed at low water. The outer rim of the crater of Totoya has a 
diameter of six miles; it slopes quite evenly from the crest of the ridge 
to the outer and inner shore line; the slopes are cut by compara- 
tively shallow valleys, separated by ridges with rounded crests. (Plates 
67, 69.) 
The water which pours into the inner basin over the barrier stretching 
across the horns of the crater finds its only outlet through the ‘‘ Gullet,” 
where it rushes through with considerable velocity. The scouring effect 
of the waters rushing out of lagoons has been noticed by all who have 
navigated among coral reefs, and the strong currents flowing out of the 
lagoons through the encircling reefs of openings are constantly referred 
to in the sailing directions. 
In the extension of the western horn of the crater on the west of the 
“Gullet,” are two small islets (Plate 68), the remnants of a part of the 
southern rim of the crater. Small islets also exist off the west coast, on 
the northern side of the isthmus. They are remnants of one of the 
spurs putting out from the west side of the outer rim. From what we 
have seen in Totoya, there is little doubt that the fringing reefs, the 
shore flats, the coral patches, and in different parts of the lagoon the outer 
reef flats are the remants of flats formed by the denudation and subma- 
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