TAHITI. 141 



the wide level platform characteristic of other Society Islands, the eroded 

 material probably accumulating only as a talus in deep water on the 

 steep declivity of the sea face. It is evident that local conditions, such 

 as occur on a small scale at Mehetia and on a larger scale at the Marquesas 

 and Galapagos, must account for the absence of coral reefs in a region 

 where they generally exist in great abundance, either on platforms under- 

 laid by volcanic rocks — as in the other Society Islands — or on platforms 

 eroded from elevated corallifei'ous limestone, as in the Paumotus and Cook 

 Islands. 



Tahiti. 



Plates 84.-S9, 202, 208-210. 



Tahiti, by far the largest and most important of the Society Islands, is 

 about thirty-three miles in length from its northwesterly point to the south- 

 eastern extremity. It consists of a principal land mass (PI. 202) separated 

 by a narrow isthmus of about one and a half miles, connecting it with the 

 eastern peninsula of Taiarapu (PI. 208, fig. 1). The main part of the island 

 is circular, slightly angular, and is Hanked on the east by a line of narrow 

 barrier reefs which extend as fiir as Artemise Bank, where it becomes broken 

 into a series of disconnected i"eef patches extending as far as Point Venus 

 (Pis. 202 ; 208, fig. 2 ; 209). At one or two points on the east side, from 

 Boudeuse Pass and Faone Pass, the barrier reef becomes more or less con- 

 nected by secondary patches with a fringing reef, which skirts irreguliirly 

 the whole eastern coast,^ except in the reaches where the shore line is 

 covered by volcanic sand beaches or coral sand beaches, or a mixture of 

 the two. On the northwestern ftice from Point Venus (PI. 209) to the north- 

 western point of the island (PI. 208, fig. 5) (Tataa Point), beginning to the 

 west of Matavai Bay, the coast is flanked by a wide reef flat forming a 

 barrier reef separated from the shore by a narrow channel, which connects 

 Matavai Ba}' with Taunoa Pass and Papiete Pass, and with the harbor of 

 Papiete (Pis. 202, fig. 2 ; 209). To the westward a continuation of the same 

 lagoon comes out at Taapuna Pass (Pi. 208, fig. 5). 



1 A. Chart 1382. 



