1898.] Funafuti, Rotuma and Fiji. 423 



exposure to the air ; on Funafuti they require constant sub- 

 mergence and we are thus led to regard their upper surface as 

 marking what was at one time the level of low tide in the swamp." 

 The species of Porites, referred to, very closely resembles Porites 

 arenosa (Esper), a very common species on the shoals in the 

 lagoon ; living Heliopora was only obtained once at Funafuti, 

 and then from a depth of over 35 fathoms off the southern reefs 

 of the atoll. The rest of the swamp is sparsely covered with 

 mud, being formed of a hard consolidated rock, which closely 

 resembles the rock forming the reef. North of the mangrove 

 swamp is a marshy pool more or less filled with brackish water, 

 and there are in the middle of the south end of the same island a 

 number of such pools ; they seem to me to be directly comparable 

 to the " barachois " of Diego Garcia 1 , described by Bourne. 



From the sea the mangrove swamp is separated by the 

 " hurricane beach," a structure which extends to some extent 

 round the seaward face of all the islands, but varies considerably 

 on account of the position of the islands in respect to the atoll, 

 and possibly from other causes. It is the extreme edge of the 

 land against which the sea, after passing over the reef, expends its 

 force. The height of its summit above the sea level at high tide 

 varies up to 7 feet, but a greater height than 4 — 5 feet is un- 

 common. Its top is covered with boulders torn from the reef 

 facing it, often much rounded and worn by the water. Near 

 its summit this beach slopes down to the sea at an angle of 

 about 30°, but towards its base, where it is washed by the tide, 

 and formed of a hard consolidated coral-rock, it passes gradually 

 into the flat reef. Its formation along the whole of the main 

 island is precisely similar to the above, but in the islands to the 

 south-east of the " pocket " there can scarcely be said to be any 

 such beach at all, and the land is broken into, and in places 

 partially submerged at spring tides. On the leeward side of the 

 atoll generally this beach, or a sudden fall from the land to the 

 high tide level, exists, but at its base the solid rock cannot be 

 seen ; instead the whole is covered by small rounded fragments 

 of reef-rock, coral, shells, etc., forming in fact a pebbly beach. 

 From the hurricane beach the land usually slopes towards the 

 lagoon with a drop of two or three feet in a few yards, and then a 

 very gradual slope. To windward of the atoll the islands on their 

 lagoon sides have usually no sharp fall, the high-tide level at 

 " springs " being marked by the extension of the vegetation. By 

 the village, however, the wash on the sandy shore has caused a 

 well-defined drop of one to two feet. To leeward of the atoll 



1 " The Atoll of Diego Garcia and the Coral Formations of the Indian Ocean,'' 

 by Or. C. Bourne. Proc. R. Soc. 1888, xliii. p. 440. 



