432 Mr Gardiner, The Coital Reefs of [Mar. 7, 



(Fig. 3), the rough zone is extremely broad being rarely less than 

 100 yards, while the reef- flat is only about 30 yards. There is 

 here practically all along a sudden drop of two feet from the rough 

 zone to the reef-flat, and along this edge there is a line of small 

 pinnacles. The -hurricane beach is formed of coarse shingle and 

 shows very distinctly in its abrupt fall the height to which the 

 tide rises. Towards the lagoon the beach is sandy ; below this the 

 lagoon platform is distinct. In the small lagoonlet, between the 

 two islands, there is found a sandstone, the strata of which dip 

 slightly towards the lagoon. It is apparently a true beach sand- 

 rock formation and only occurs in this position. I have appended 

 a section (Fig. 3) across the island of Pava, showing the general 

 features of the rim of the atoll here. 



The reef, except where it is broken by the deep channels before 

 mentioned, is continuous round the whole lagoon, and connects all 

 the islands with one another. The rim and reef-flat show no 

 discontinuity, the reef-flat, continuing between the islands, and a 

 little lagoonwards ending in a straight cliff exactly similar to that 

 of the lagoon platform of the islands. The reef between the 

 islands slopes a little towards the lagoon, so that, even at extreme 

 low tide, a small quantity of water makes its way over it into the 

 lagoon instead of flowing out again through the fissures, which 

 run through the rim. Probably owing to the difficulty of fixation 

 found by the larvae, few corals grow on the reef in such a position. 

 To leeward the reef is often very broad, as indeed are the inter- 

 spaces between the several islands, and is generally exposed 

 slightly at extreme low tides. Often its lagoon edge extends 

 continuously with that of the lagoon platform of the islands, and is 

 much broken up into knolls and patches, on which corals and 

 nullipores flourish luxuriantly. South of Fuafatu, the reef has a 

 distinct channel in its middle a few fathoms deep, extending along 

 for some distance it consists of an outer reef with a distinct row of 

 pinnacles marking its position at low tide, and an inner reef, a 

 broad flat platform, a continuation of the lagoon reef of the island 

 itself. South of this both reefs have a distinct but narrow passage 

 to the ocean beyond ; this passage through the outer reef is 

 nothing more than a long fissure with a depth of about 2^- fathoms, 

 and is just broad enough to take a boat through. North again of 

 the same island and generally to the westward, the reef has a 

 depression in the centre, but it is not usually more than a few 

 feet deep. 



The shoals in the lagoon commonly on their upper surface, 

 resemble very closely the inner parts in relation to the atoll of 

 the lagoon reef, and the same species of coral are found on both. 

 About the centre of the lagoon is one large shoal, and there are 

 many others, which lie mostly on the windward side and towards 



