“ 
AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 95 
slight angle with the west coast ridge, and is separated from it by a deep 
valley. The three islets off the western part of the southern face of 
Mango are all on the outer edge of the reef flat (Plate 87). They con- 
sist of volcanic rocks. The central 
islet is the largest, and is com- 
posed in part of stratified volcanic 
mud underlaid by harder rocks. 
Between the islets, and extending 
over the outer reef flats to the 
north and to the east, stretch 
numerous negro-heads of a vol- 
canic nature. 
The island of Mango is of the 
same type as Fulanga, except that 
the erosion and denudation of the 
lagoon has not been carried on to 
so great an extent, Mango being 
composed so largely of harder 
voleanic rocks. The platform 
forming the reef flat is dug out into a very narrow and shallow lagoon, 
and both are studded with negro-heads, the remnants of the adjacent 
shore slopes. The inner sound, which in the case of Fulanga has been 
eroded and denuded to form a large inner basin, consists in Mango only 
of a diminutive basin studded with elevated limestone heads and rocks, 
and barely connecting with the exterior eastern lagoon ; the sea has not 
WEST OF MANGO LANDING, VOLCANIC 
SUBSTRATUM. 
found its way to any extent through the elevated limestone barrier lying 
across the break of the rim of the island. 
Lakemba. 
Plates 19, 21. 
The island of Lakemba is elliptical, with a prominent spit extending 
off its southern face. Its greatest diameter is about five miles and a 
half. The central mass of the island, which rises to a height of 720 
feet, is volcanic ; on the flanks of this, on the northwestern and western 
sides, are found nearly vertical steep shore bluffs of coralliferous lime- 
stone elevated to a height of from 200 to 250 feet. The ridges extending 
along the south shore, separated by a spur from the central mass, also 
consist of elevated reef rock. Lakemba is surrounded by a fringing 
reef, narrowest off the northwestern point of the island; it widens 
