1898.] Funafuti, Rotuma and Fiji. 429 



extent as to silt up certain parts of the lagoon. This and the 

 abundant growth of corals and calcareous algae, such as Halimeda, 

 lead to the belief that the lagoon is slowly filling up." I shall 

 have occasion later to refer again to this paragraph ; here I am 

 merely drawing attention to it as showing the nature of the sand. 

 It is only in this one situation that I failed to find a solid gently 

 sloping platform of rock extending from the islands into the 

 lagoon ; in some places its nature is to some extent disguised 

 near the shore by a deposit of sand, but its presence is everywhere 

 clearly indicated. Its surface is smooth, but somewhat broken up 

 into holes, which generally increase in size with the distance from 

 the land ; it is also in places strewn with boulders. After a 

 gradual slope, to a depth of about 6 feet at low tide, it commonly 

 ends in a cliff, or wall, soundings from the edge of which give 

 depths of 2 — 5 fathoms, or even more. Such parts of it, as lie 

 below the low tide level, are covered with green algae, Sar- 

 cophytum, sponges and foliaceous nullipores ; corals too are fairly 

 abundant on its extreme outer edge. Denser nullipores are also 

 found belonging for the most part to species with upright plates, 

 or round mamillated projections; great bunches of the genus 

 Halimeda are very common. Sarcophytum is found in great flat 

 spreading masses, but its distribution and that of corals over this 

 area depend largely on the position of the lagoon-reef in respect 

 to the openings in the atoll-reef, currents, etc. 



The outer reef varies to an extraordinary extent, but every- 

 where the rim and the reef-flat present similar features to those 

 already described for the windward side. The inner rough zone 

 on that side is generally narrow and fairly even in height, but in 

 places on its inner part just at the base of the hurricane beach 

 isolated pinnacles of rock occur. These clearly form part of the reef- 

 rock below them, and consist of similar constituents. The largest 

 have a diameter of 6 x 6 feet with a similar height ; their tops 

 often to some extent overhang their bases. At high tide they 

 are washed by the waves, but stand up for 1 — 2 feet above the 

 tidal level. By this wash of the waves they are sometimes 

 eaten into in such a way that the softer rock between the harder 

 coral skeletons has been removed, leaving the corals freely ex- 

 posed. The genera Millepora and Madrepora can commonly be 

 identified ; I also found the laminae of Heliopora. The branches 

 or laminae of these corals generally grow straight upright in any 

 position, in which they are well covered at low tide. Their 

 skeletons, in the few places where I could trace them satisfactorily, 

 I found invariably standing on these pinnacles in the same 

 position. Such would not be the case were these pinnacles 

 formed in a hurricane beach by the consolidation of fragments 

 and the subsequent solution of the parts of the beach round them. 



VOL. IX. PT. VIII. 35 



