HEREHERETUE. 131 



running more or less at right angles to the outer edge of the reef flat, where 

 the Nullipore knolls form an almost unbroken abrupt vertical wall. 



Some of the sand dunes have been di'iven into the lagoon, killing the 

 Pandanus and other vegetation, while other dunes are stationary, being 

 overgrown with grass and scrub vegetation ; the beach forms a grass-topped 

 bank which extends into the vegetation of the interior of the land rim. 

 Coral rubble and shingle is also blown and washed in places partly across 

 the islands. The base of the islands is mainly composed of beach rock 

 resting upon the old ledge, which crops out on the reef flats. In the 

 Gloucester group, where the rubble or beach rock has been washed away, 

 the old ledge forms the floor of the reef flats wherever we have examined 

 them. 



Hereheretue. 



Plates 79-83, 201, 203. 



Hereheretue encloses a lagoon about three miles in diameter, without a 

 boat entrance. The western half of the land rim consists of a wide reef flat, 

 bare at low water, in the central part of which is placed a small island with 

 a few cocoanut trees. On the southwestern face of the land rim a few sand 

 bars have been thrown up. 



On the east face of this atoll are a great many dead trees and bushes 

 which have been killed by the inroad of the beach sand blown inland 

 (PI. 81), and along the sea face of Hereheretue, where it is not covered with 

 grass (PI. 80), blown sand is seen to extend under the trees and shrubs. On 

 the north end of the east face of the atoll there is a good exposure of strati- 

 fied beach rock running along the base of the high sand beach, which miist 

 be from eighteen to twenty feet in height (PI. 81). At the northwest horn 

 sand and shingle bars extend across the wide gap separating two of the 

 islands ; a high dune has also been formed there, the greater part of which 

 is overgrown with vegetation. 



The seven islands to the south are almost connected, the gaps between 

 them allowing but little water to flow across into the lagoon except at high 

 tide. The islands are all eds-ed with sand beaches on the lao-oon side. The 



