88 THE CORAL EEEFS OF THE MALDIVES. 



or atoll with a wide-rimmed reef flat that has only reached the surface, close 

 to the horns of the island. The rest of the rim flat is submerged, leaving 

 the lagoon open for the whole width of the faro, with as much as five 

 fathoms of water on parts of the rim. The principal island of Dureadu 

 is clothed with luxuriant vegetation ; at the extremity of the eastern 

 horn rises a small island covered with large bushes and separated from 

 the principal island by a line of large coral boulders. The east face of 

 the islet and of the principal island is flanked by a shingle beach with 

 stretches of small coral boulders which extend also on the northern face 

 of the main island of the atoll. The lagoon of Dureadu is one of the 

 deepest of the small independent atolls in the Maldives ; it is fully a mile 

 across with a depth of eighteen fathoms. Dureadu resembles Nalandu, 

 though the lagoon of the latter is much smaller and its greatest depth 

 is not more than two fathoms. 1 



All the islands we passed on the east face of Miladummadulu are steep 

 to ; there are no reef flats or spits extending from the flats on the lee side, 

 as in the islands of many of the other groups. The original flats must have 

 been limited to the areas now occupied by the islands or faros. 



Ekasdu (Pis. 42, fig. 2 ; 43) is perhaps the most advanced stage of an 

 enclosed central lagoon. It could be well seen from aloft. The outer 

 beaches are all steep coarse shingle slopes. The lagoon of Ekasdu is of 

 a dark blue color, indicating a depth fully as great as that of the lagoon 

 of Bodu Mandu with a greatest depth of five fathoms. 



Ereadu, the next island to the north, though less than a mile in diameter, 

 is the largest of the chain of small islands between Kuludu and Furnadu 

 on the east face of Miladummadulu. The crescent-shaped island, open 

 to the west, encloses within its horns an elliptical lagoon, shallow at its 

 southern extremity with a wide shallow western rim over which the sea 

 flows freely into the lagoon ; parts of the rim are barely awash. Ereadu 

 represents one of the earliest stages in the closing off of a lagoon where 

 no dam or shingle heap has as yet been thrown up on the reef flat between 

 the horns. 



1 Of the central islands it was only at Dureadu that Gardiner found on the northwest face the exist- 

 ence of a definite but very limited reef flat with a well-formed fissure zone of gradual slope to the 

 general level, loc. cit., p. 388. 



