TAEITAEI. 267 



The dam or ledge on the outer sea face (PI. 158, fig. 2) was composed of 

 huge masses of coral beach rock and conglomerate piled up in endless con- 

 fusion, forming moimds of different heights, more or less connected (PI. 158, 

 fig. 1); on some of these the inner side, or sometimes the upper part of 

 the dam had been weathered and worn and honeycombed and broken into 

 sand sufficiently fine to allow vegetation to obtain a foothold. Here and 

 there we found little tufts of low bushes and shrubs growing on the summit 

 of the outer dam, as they once began on the summit of the inner row of 

 islands (PL 157, fig. 2); these have gradually become connected either by 

 the formation of dams from the inside of the lagoon, or by the building 

 up of the main dam on the outer edge of the reef flat ; this has changed 

 the gaps between the islands, which once connected the lagoon with the 

 outer sea, into bays opening either on the sea face or on the lagoon face 

 (Pis. 153; 156, fig. 1; 157). 



The shores of the sand bars and spits of the islands and islets and the 

 inner shore lines of the gaps or of the bays were generally covered with 

 masses of dead shells. From the number of dead tests of Metalia, 

 Echinoneus, Laganum, and Spatangus mixed with the shells, they must 

 live in great numbers in the shallow and protected waters on the bay side. 



The changes going on at certain points of the great outer sea dam show 

 that the material piled upon the outer sea face gradually becomes broken 

 and ground, and forms first a shingle beach, and finally a fine coral sand 

 beach. Nowhere is there a better example than at Taritari of the process by 

 which additions are made to the land rim, and material is thi'own up on 

 the flats, both on the sea face and on the lagoon face, and of the formation 

 of secondary lagoons, of huge bays or small gaps, by the gradual cutting off 

 of extensive areas of the reef flats, and their isolation under conditions 

 due to the prevalence of the trades, and to the general direction of the 

 wind, both on the lagoon side and on the sea side. 



In Keuea gap the flat is covered with dead Millepores. the interstices 

 between them must have been rapidly filled by sand and ooze, by fragments 

 of dead shells, and Nullipores ; the whole became cemented, leaving only 

 here and there an occasional Millepore head cropping up above the general 

 level to indicate the character of the corals which iiave built up the 



