APAMAMA. 241 



formed in the gaps on the sea face of the land rim and not on the inner 

 face, as we have described them for Tapetenea. Some of the gaps, instead 

 of being closed on the sea face, are closed on the lagoon face (PI. 139, 

 fig. 2), forming at first a bay into which the waters pouring over the outer 

 edge of the reef fiat platform have free access. Gradually as the currents 

 which once passed into the lagoon have been shut off, sand accumulates on 

 the two sides of the bay, and is forced towards the outer edge of the reef 

 platform. So that a part of the reef platform, once a bay, is now separated 

 from the adjoining district by a spur or spurs from the islands once flanking 

 the gap leading into the lagoon. These spurs, however, do not consist 

 mainly of sand, as they do on the lagoon side, but are made up generally 

 of coral rock shingle, and smaller fragments of coral, with comparatively 

 little sand, though, according to local conditions, these ledges are often 

 covered with fine coral sand. The bottom of the bay flanking the lagoon 

 is almost always a low sandy beach ; it has been formed much in the same 

 manner as the adjoining islets on the outer reef flat, by the throwing out of 

 sandy spurs on their opposite faces. 



On some of the spits forming the boundary of the platform lagoons, the 

 reef rock platform has occasionally been elevated at least a couple of feet. 

 Here and there we also find outliers of the old ledge forming low vertical 

 walls from three to five feet in height ; they are undercut, and the spaces 

 between them have been filled either with beach rock, or conglomerate, or 

 with coarse shingle or with sand. 



Pandanus trees are comparatively rare on the east coast of Apamama, 

 but there are a large number of Pisonias and cocoanut trees, and, in some 

 cases, beautiful hardwood trees. Some of the higher beaches look like 

 dunes covered by vegetation, and in this way long wide beaches have per- 

 haps been formed. We found large masses of driftwood on the eastern side 

 of Apamama. 



Towards the southern horn, on the eastern face of the land rim of 

 Apamama, numerous islands and islets are found in the lagoon bays with 

 intricate passes between them. The islands run more or less parallel with 

 the outer reef flat. They indicate the former existence of a number of 

 old gaps now shut out from the sea by the bars of rubble and of sand which 



16 



