KUSAIE. 33 



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of mangroves (PI. 229). At the southern extremity of Kusaie, near 

 Cape Tupinier, large angular boulders of coral reef conglomerate were 

 thrown up on the spits, supplying the material for the coral shingle 

 beach which characterizes the sea face of the belt of mangrove islands 

 separating the inner lagoon from the outer lagoon. The flats and islands 

 of the inner lagoon have been formed by the accumulation of volcanic 

 sand, washed down from the adjoining slopes, and forming patches upon 

 which the mangroves have taken root. The patches are often separated 

 by deep lanes of water, in which corals may grow ; where corals have 

 been overwhelmed by the volcanic sand they form disconnected patches. 

 Thus has been built up the inland labyrinth of mangrove islands which 

 reaches from Port Lottin not only lound the south shore of Kusaie, but 

 also on the eastern, as well as the western and northwestern faces of 

 the island (PI. 229). 



The reef flat to the eastward of our anchorage is covered with large 

 patches of beach rock conglomerate ; on their slopes corals were grow- 

 ing in profusion^ and mangroves had, here and there, taken possession 

 of islands or islets disconnected, as yet, from the labyrinth of islands 

 forming the inner belt of the reef flat. We examined the channel leading 

 among the inner belt of mangrove islets, on the east side of the harbor. 

 The channel runs at least five miles parallel to the shore line, is from 

 three to six feet deep, meandering in all possible directions, and sending 

 off branches at right angles, forming an anastomosing belt of channels 

 as far as Cape Tupinier. There are an endless number of water lanes, 

 with ample depth for their canoes, which the natives use in passing 

 from one part of the island to the other, inside the barrier reef. The 

 mangrove trees take here an enormous size, many of them being between 

 forty and fifty feet in height, and their branches, together with those of 

 the Fetaus, the Poukas, the passion flower trees, and other hardwood 

 trees, form an immense arch which sometimes covers the channels so 

 completely as to make a tunnel through which the canoes or boats may 

 pass (PI. 186). The main channel of the lagoon runs along the base of 

 the volcanic slopes of Kusaie ; it is separated from them by numerous 



small mangrove islets, covered with volcanic mud, which finds its way 



22 



