PRELIMINARY REPORT. 25 



deep. Some of the smaller islets we visited, among which are Tikei, 

 Aki-Aki, and Niikutavake, have no lagoons. The former has a small 

 shallow sink in which fresh water collects, but the rim is only very 

 slightly higher than the interior. The last two islets are apparently 

 depressed in the centre, three to four feet below the outer bank of sand 

 which forms the rim (about ten to twelve feet high) of the basin of the 

 island. I was at first inclined to look upon these islands as examples of 

 islands which had been cut down to the level of the sea and subsecjuently 

 been built up by beach rock and sand in the manner described above. 

 The existence of extensive sand dunes on two sides of the island at 

 Pinaki, and of large dunes (estimated to be thirty-five feet high) on 

 the south shore of Nukutavake, seems to indicate the possibility of 

 there having been a shallow lagoon occupying the centre of Aki-Aki 

 and of Nukutavake, and that these lagoons were gradually filled by the 

 sand dunes, nuich as Pinaki is filling now. 



At Pinaki (Whitsumlay Island), there is no doubt that the lagoon is 

 rapidly filling from the sand blown in by the dunes. They are from 

 twelve to fifteen feet high, and are forcing their way in towards the 

 lagoon, killing the pandanus and whatever vegetation there is growing on 

 the land-rim of the lagoon. The dunes have probably filled also a 

 second entrance to the lagoon, indicated now only by a somewhat lower 

 level of the land-rim. Dr. Moore and Mr. Towusend, who went ashore 

 at Pinaki, report that the lagoon is not more than three fathoms deep ; 

 they could wade over the greater part of it. Mr. Alexander counted no 

 less than 116 islets in this small lagoon — less than a mile in diameter — 

 islets formed of masses of dead Tridacna shells thrown up on ledge rock, 

 on the slopes of which grew madrepores. The bottom of the lagoon is 

 covered by Tridacna, and masses of a species of Area live near the edge ; 

 the intervening spaces being filled with nullipores. The entrance to 

 the lagoon is perhaps 150 feet wide, and there is a cut through the beach 

 rock covering the old ledge giving access to the sea into the lagoon at 

 certain stages of the tide. The water in the lagoon is quite warm. 



At Pinaki. as at other atolls and islets to the eastward, there are 

 fewer cocoanuts than on the westward atolls, and the vegetation consists 



