TARITAEI. 265 



ment of huge square or oblong or irregularly shaped masses of coral, with 

 flat tops, on which were growing Nullipores. Between these blocks was left 

 a labyrinth of passages or of narrow lanes covered with fine coral sand, the 

 depth of which varied from two to three feet of water. At low-water mark 

 one could walk across, on the top of these blocks, from one to the other, and 

 thus reach the sea face of the dam thrown up by the sea on the outer edge 

 of the reef flat, and partly derived from the breaking up of elevated modern 

 reef rock. The secondary lagoon behind the dam (PI. 158, fig. 1) is about 

 200 feet in width, and extended from the northern side of Keuea gap as far 

 as the southeast point of the main island of Taritari (PI. 224, fig. 4) ; the 

 outer dam forming a barrier to what might be called a platform barrier 

 reef lagoon, which varied greatly in depth according to the level of the 

 underlying reef flat platform. On the west face of this secondary lagoon 

 the shore beach of the island forming the land rim (PI. 157, fig. 1) is 

 about eight feet in height, and slopes very gradually towards the lagoon 

 face, where we come upon the continuation of the reef of Millepores we 

 have just described, which has been covered by this inner dam (PI. 155, 

 fig. 3). The Millepore reef fiat must once have extended out from the east 

 face of the land rim, before the existence of the great dam now forming 

 the breaker to the disintegration of the existing islets of the land rim. 



There must have been a time when the Millepores were abundant in the . 

 outer secondary barrier reef lagoon, and when those on the wide lagoon reef 

 flat were connected with them, as they are now connected in the gaps be- 

 tween the islands, before a part of the Millepore flat was covered by the 

 material thrown up on the higher parts of this immense fiat, both from 

 the lagoon side and from the sea face. As the Millepores cropped up at 

 the surface, the labyrinth of passages between the clusters became gradually 

 filled, as fast as the tops died and were broken off by the action of the 

 sea or from other causes. The Heliopora reef described by Mr. Henley and 

 Professor Sollas at the eastern horn of Funafuti owes its origin to similar 

 causes. There was a time when the different belts of the island itself held 

 to the lagoon the same relation which the outer breakwater now holds to 

 the secondary platform lagoon, formed between it and the outer breakwater ; 

 as we walked across the island (PI. 157, fig. 1), we observed in several direc- 



