112 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



and the shape of its ridges, crests, anti 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 bai-rier 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 j-eef 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 



