156 "ALBATEOSS" TROPICAL PACIFIC EXPEDITION. 



Narrow shore platforms cut into the volcanic rocks of the points and 

 headlands along the shore of Matavai Bay. The volcanic sands extend to 

 the east of Point Venus to Brander's Bay ; the flats formed from the dis- 

 integration of the land are all composed of it, as well as the islands and 

 islets to the east of Brander's Bay (Port Motu Au, PI. 209). 



It seems to have escaped Dana as well as Wilkes and Messrs. Le Clerc 

 and de Benaze, that Captain Beechey in 1836 also attempted to obtain some 

 data regarding the rate of growth of corals on Dolphin Bank.^ He says 

 that " from the reports of the natives the coral bordering the volcanic islands 

 does not increase very fast, as we never heard of any channel being filled 

 up. The only direct evidence which I could obtain of this fact was that 

 of the Dolphin Bank off Point Venus in Otaheite. This reef, when first 

 examined by Captain Wallis in 1769, had two fathoms of water upon it. 

 Cook sounded upon it a few years afterwards, and gave its depth fifteen 

 feet. In our visit to this place we found upon the shallowest part of it 

 thii'teen feet and a half. These measurements, thoiigh at variance from 

 the irregularity of the surface of the reef, are sufficiently exact to warrant 

 the conclusion that it has undergone no material alteration during an inter- 

 val of fifty-six years." Beechey also noticed that the Dolphin Bank was 

 in a bay into which several rivers flowed, which would materially influence 

 its growth. 



Murea. 



Plates 90, fig. 1 ; 91 ; 208, fig. 6. 



The island of Murea, distant from Tahiti about nine miles, is more broken 

 in outline than Tahiti; its sharp peaks assume most fantastic outlines (PI. 91, 

 fig. 1). Seen from the north, two wide valleys, separated by Tea Promon- 

 tory (PI. 208, fig. 6), form deep harbors extending for more than a quarter 

 of the depth of the island towards the interior. They open out into the 

 wide amphitheatre from which run the spurs and ridges which extend to 

 the eastern and western sides of the island (PI. 91, fig. 1). The island is 

 triangular in shape, each side being about nine miles in width, and is 



1 Beechey, loc. cit., Vol. II. p. 190. 



