KUSAIE. 335 



series of small islands at right angles with the outer beach. This mangrove 

 belt is a most characteristic feature of the barrier reef of Kusaie. The man- 

 groves grow upon a labyrinth of low islands (PI. 229), formed of material 

 washed down from the hills immediately behind the shore line ; this mate- 

 rial is mixed with coral rock material thrown up by the waves on the outer 

 broad reef flat which we were skirting. The beaches of the outer mangrove 

 islands are composed either of coral shingle or shingle composed in part of 

 beach rock conglomerate and in part of volcanic rock. 



As we approached Cape Tupinier, the southern point of the east face of 

 Kusaie, we could see the rounded bluffs forming the termination of the spurs 

 extending towards the southern reef flat of the island, with deep valleys 

 running towards the interior separating them. From the base of the 

 spurs beach rock and volcanic boulders extended over the reef flat in huge 

 spits (PI. 229) ; on these grow the mangroves which form so characteristic 

 a fringe to that part of Kusaie (Pis. 184, figs. 1, 2 ; 185, figs. 1, 2). They 

 recall the belts of vegetation we have observed in some of the Society 

 Islands, especially at Bora Bora, where the vegetation, instead of con- 

 sisting of mangroves, was principally made up of cocoanuts and the usual 

 reef bushes. At Kusaie the vegetation at the base of the volcanic slopes 

 consists of magnificent forest trees (PL 186) ; they also extend over the 

 mangrove islands and islets and give to the belt a different aspect from 

 that which characterizes the belt of vegetation on the outer reef flat of 

 the Society and Fiji Islands. 



A similar belt of mangroves skirts the greater part of the northwestern 

 coast; from Cape Halgan, the northern point of the island, it extends both 

 west and south, and thus forms a nearly continuous belt around Kusaie, 

 interrupted only at some point where the barrier reef flat is rather narrow, 

 or where the barrier reef becomes a fringing reef (PI. 229). The greatest 

 width of the reef flat is about a mile ; a number of basins are formed by 

 projections of the spurs from the volcanic slopes to the outer edge of the 

 reef flat, especially between Port Lottin and Cape Vauvilliers (PI. 229). 

 The islands of Lele and Yenas are the remnants of the spur which once 

 ran from Mount Buache to Point D'Urville (PI. 229). 



It is evident, from the position of the volcanic rock outliers and from 



