154 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



into Matavai Bay. Dolphin Bank (PI. 209) is the only remnant of that 

 ridge; but its higher points consist entirely, as I have mentioned before, of 

 small heads of corals covered with NuUipores. To the west of the entrance 

 of Papiete, the barrier reef flat is much wider than the eastern flat and 

 covered with negro-lieads ; it extends in a westerly direction about four 

 miles (PI. 209). The reef flat is over half a mile in width, having only 

 a narrow lagoon channel widening out towards Torea Point (PI. 208, fig. 5). 

 There the barrier reef turns a sharp angle and runs parallel with the western 

 shore in a southerly direction ; it is separated by a narrow lagoon from the 

 fringing reef flat, which is a mass of dead corals cemented by NuUipores ; 

 the lagoon cuts through the barrier reef and forms the pass of Taapuna. 

 The reef flat to the south of the pass gradually becomes a fringing reef which 

 extends beyond Atiue as far as Acua. The shore beaches are composed 

 mainly of volcanic sand with a small admixture of coral sand. 



The island of Tehiri is an outlier of one of the volcanic spurs off Torea, at 

 the northwest angle of Tahiti ; it is in the very centre of the fringing reef 

 flat which extends from Nututere Point, south of Papiete as far as Torea. 

 Its position, as well as that of Tataa Point, indicates the manner in which 

 the fringing reef flat has gradually been formed, from the erosion of the 

 spurs extending out from the main mass of the island towards the sea (PI. 

 208, fig. 5). The islands in the northeastern part of Papiete Harbor, 

 Motu-uta, Fareute Point, and the isolated flats and bars found in the lagoon 

 channel between the barrier reef flat and the fringing reef flat, as well 

 as other points extending out towards the sea between Papiete and Point 

 Venus, are the remnants of eroded volcanic spurs and ridges whicli once 

 formed the continuation of the main slope of Tahiti (Pis. 84 ; 87, fig. 2 ; 209). 



We visited Point Venus to examine the level marks of Wilkes and 

 of Messrs. Le Clerc, Lieutenant de Vaisseau, and de Bt5naze, naval engineer, 

 relating to Dolphin Bank.* Wilkes' levels were taken on September 22, 1839, 

 and those of Le Clerc and de Benaze in September, 1869.- The level of 

 Dolphin Bank, according to Wilkes, was 7.80 ; according to the French 

 engineers it was 7.25 ; making a difference of .55 metres in thirty years. 



1 We found the stones and marks as described. 

 ^ Report published in Paris, June 29, 1870. 



