MANGA REV A. 



67 



vegetation flourishes, extends along the outer face of the reef flat, which 

 varies from fifty to one hundred and fifty yards in width, and is flanked 

 at the base by low buttresses of modern elevated coral reef rock and 

 of breccia in places, all more or less weather-beaten and honey-combed 

 (Pis. 83-88). 



The islets and their formation (PL 91) and their junction or division 

 into larger or smaller islets, and the gaps which separate them (Pis. 79, 82, 

 83, 89), the mode of formation of the buttresses (Pis. 85, 86) of the planed- 

 off, hard, nearly level, reef flat (Pis. 84, 86) of tlie corralline mounds of the 

 outer edge (PI. 84), all these diifer in no way from what has been described 

 in other barrier reef islands and atolls of the Pacific. 



Nativk Hut o.\ Outer Enciuclino Reef. 



The beaches of the lagoon are steep (PL 81), and corals do not seem to 

 thrive in those parts of the lagoon to which the sea does not have access or 

 are at some distance from shore. This is well shown by the vigorous growth 

 of corals in the fringing reef to the south of Mount Duff on the outer edges 

 of the reef patches of Port Rikitea, and on the spits which connect Au 

 Kena with Manga Reva, in contrast with those along the west face of the 

 lagoon flats to the west of the eastern barrier reef. 



There is a northeast horn of the eastern barrier reef in the extension of 

 Manga Reva Island, forming the northern culmination of the central bight 

 of the eastern face of the encircling reef (PL 14). From that point the reef 

 flat runs westerly to form the northern horn about three miles north of 

 Manga Reva Island. The position of the outer reef cannot be correct on 

 the chart (II. 0. No. 2024). On leaving Manga Reva we made three sound- 



