112 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
and the shape of its ridges, crests, and peaks (Plates 33, 34) shows the 
effect of extensive denudation and erosion. The island is elliptical, eight 
miles long, and about six wide. Moturiki flanks Ovalau on the southwest 
side, is low, about five miles long, and connected with the southern face 
of Ovalau by an extensive fringing reef flat surrounding its eastern face 
and the islands of Yanutha Levu and Yanutha lai lai. The Moturiki 
fringing reef is separated from the barrier reef by a narrow channel, and 
the northern extension, forming the barrier reef off the east coast of Ovalau 
(Plate 20°), is broken by a number of deep openings (Plate 7). The 
bottom of the lagoon is made up of coral and coralline sand, compara- 
tively little mud being washed down from the hill slopes, the water inside 
the lagoon being quite clear. From the inner edge of the barrier reef 
run out a large number of very flourishing coral patches in from two to 
three fathoms, and extending to seven or eight. The reef flat is in some 
places more than half a mile wide (Plate 20°, Figs. 1-5). A good many 
NEGRO-HEAD, LEVUKA BARRIER REEF. 
negro-heads are scattered upon the reef flats, some of them of consider- 
able size. The average depth of the narrow lagoon separating Ovalau 
from the barrier reef is from nine to fifteen fathoms, but in some places 
there are short stretches with a depth of from sixteen to twenty 
fathoms. 
Between the Na lulu and the Ngava Passages (Plate 7) an extensive 
flat connects the barrier reef with Ovalau, much as the fringing reef of 
