114 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



The stretch of strata of volcanic mud constituting the east shore of Viti 

 Levu north of Mbau undoubtedly once extended farther east, connecting 

 the main island with the islands of Moturiki and of Ovalau. This readily 

 explains the changeable character of the barrier reef at different points 

 along the coast of Viti Levu. Off Ovalau and Moturiki the substructure 

 of the barrier reef is volcanic, and the negro-heads which crop out upon 

 its surface at various points plainly indicate this. One of the most 

 striking of these protrusions being a small mushroom-shaped volcanic 

 rock on the barrier reef to the south of Moturiki, immediately west of 

 Thangalai Island (Plate 7). This island and Leluvia, and one or two 

 keys on the northern part of the great reef south of Moturiki, are small 

 islets of coral sand thrown up on some of the shallower parts of the reef 

 flats. The larger islands are thickly covered with cocoanuts and shrubs. 

 On the southern part of the reef flats immediately north of the Tombe- 

 rua Passage near the exterior edge is the island of IMumbualau. It is 

 about thirty feet high, and is composed of elevated corallifei'ous limestone 

 deeply imdercut, pitted, and honeycombed, while the islands farther 

 inland off Kamba Point consist of stratified volcanic mud. 



Another very striking fragment of elevated coralliferous limestone is 

 that of Na Vunivatu (Plate 37), on the reef flats to the south of Xasilai 

 Mouth. The remnants of the elevated reef can be traced south of Tom- 

 berua Passage on the Nasilai reef flats, and extend on both sides of the 

 lighthouse. There ai'e numerous heads of elevated limestone, fragments 

 of former large stretches of the same material. Still farther south the 

 elevated coralliferous limestone is seen to underlie the island of Nukulau 

 (Plates 38-41) at the mouth of Lauthala Harbor (Plate 25), as well as 

 the flats to the eastward and the island of Mokaluva with its flat (Plate 

 38). The extensive mud flats forming the mouth of the liewa River 

 have to a gi-eat extent encroached upon the inner edge of the coral 

 reef flats underlaid by the elevated coralliferous limestone which every- 

 where crops to the surface to the south of Tomberua Passage. As far 

 as the Nukulau mouth of the Rewa, the reefs are in reality fringing 

 reefs growing upon flats of elevated coralliferous limestone, intersected 

 by deep indentations forming reef harbors. The great extent of the flats 

 skirtins: the shore of Viti Levu eastward from Suva Point shows the 

 amount of denudation and erosion to which this part of the island has 

 been subjected (Plates 24, 25). From off Lauthala Bay (Plate 25) to 

 Suva, the reefs are extensive barrier reef flats separated by passages 

 leading into the channel running between the barrier and the shore 

 (Plate 7). Some parts of the barrier flats are more than a mile wide. 



