BY C. HEDLEY. 459 



of Turbinaria have come to rest in the position of least resistance, 

 the stem upwards, the basin down. The more fragile madrepores 

 are only present as broken fragments. No living coral is seen at 

 all on the reef crest, which is one long unbroken sepulchre of 

 actinozoan life. 



On the north side the nigger-heads were about twelve feet 

 .above low spring tide level. The outside of the reef descends 

 this depth in places as a flight of shallow irregular pools and 

 terraces, which reminded Mr. Grant and myself of the terraces of 

 sinter which accumulate below a hot spring. When the lagoon 

 has almost run dry, the shallow heated water is likely to hold an 

 unusually large amount of lime in solution and to thus deposit it. 

 The outer slopes of the reef are not encumbered by much coral, 

 either dead or alive. On the leeward side they are grassed with 

 green seaweed. 



The crest of the reef acts as a dam-head to impound the waters 

 of the lagoon from half-ebb to half-flood. No continuous barrier, 

 however, stops the outflow of the water, which is merely choked 

 and obstructed by the dead coral mass strewn along the crest. 

 While the tide is down, the lagoon water trickles and dribbles 

 away on all sides; here and there it finds a byewash through 

 which it streams more freely. 



So far as we could explore it, the lagoon floor is carpeted 

 throughout with living coral. The coral takes the form of tables 

 or dwarf hedges composed of interlacing masses of Madrepora, 

 Pocillopora, Porites, Turbinaria and Seriatopora, in which odd 

 Fungia may be entangled. These project from a level layer of 

 foraminiferal sand to a height of one or two feet. One may walk 

 continuously along the summit of a coral hedge for a hundred 

 yards. From another such it may be parted by a sandy lane. 

 The flattened tops of these corals are usually dead, and just 

 project above water when, at quarter-flood, the lagoon is at its 

 lowest. In places drifting sand had filled in the lanes and 

 smothered the coral hedge. The lagoon impressed me as fast 

 filling up. 



