122 bulletin: museum of compaPwATIVE zoology. 



feet. It resembles Xaiau on a smaller scale. It is surrounded as is 

 Tuvutha by a narrow outer reef flat, becoming a fringing reef at several 

 points of the shore, and enclosing a narrow and shallow lagoon full of 

 rocks and patches. 



There are also a number of atolls presenting no special features. To 

 the westward of Xgele Levu are two reefs, Thakau Yutho Vutho 

 and Thakau Mata Thuthu (Plate 17). The former is separated from 

 Kgele Levu by a channel eight miles wide, with 1-45 fathoms in mid- 

 channel. The latter is separated fz-om Thakau Yutho Yutho by a 

 channel 171 fathoms deep and three miles wide. The lagoons have 

 respectively a greatest depth of 15 and 19 fathoms. They both have 

 navigable entrances, and the outer reef flats are studded with negro- 

 heads and coral patches, and there are no islands on the rim. These 

 atolls resemble Ngele Levu, but are not more than one third of its size. 



It is interesting to note that to the westward of Thakau Mata Thuthu 

 (Plate 17) there is an isolated bank with 74 and 76 fathoms of water, 

 but separated from it by a narrow channel ; it n^xy be a spur of the 

 bank upon whicli the atoll of Thakau Mata Thuthu is situated, similar 

 to Cock's Bank, which is close to the southwestern edge of the 100 

 fathom line. 



Similar atolls and varying gi'eatly in shape are Duff"'s Reef (Plate 18) 



to the west of Wailangilala, and to the south Dibble's Poef (Plate 19), 



to the east of Yanua Mbalavu, Xuku Thikombia (Plate 19), and Male- 



vuvu Reef (Plate 19) ; farther south Thakau Tambu, Yaroua, and the 



smaller reefs Thakau Nokeva and Thakau Lasemarawa (Plate 20). 



As we steamed from Tuvutha to Xaiau we saw the sandbank in the 



centre of Tavanuku i vanua Reef surrounded by a fringing reef somewhat 



more than a third of a mile in width (Plate 20). To the southwest of 

 « 



Tuvuthci is also situated a small circular atoll, Tavanuku i wai, with 

 an outer reef of about half a mile in diameter enclosing a small shallow 

 lagoon. 



To the east of Mothe are Thakau Motu (Plate 22), a large atoll open 

 to the west, \nth 24 fathoms in the deepest part of the lagoon (Plate 

 23% Fig. 6), and Thakau Yau (Plate 22), a small circular reef with a 

 shallow lagoon of impounded water. Xeither of these did we visit. West 

 of Ivomo, Thakau Yuite (Plate 22), in a line running north and south, 

 east of the Yangasa cluster, lies Thakau Levu, and southwest of Yanua 

 Yatu and to the northeast of Totoya the Tova or Xa Yatu Reef (Plate 

 23% Fig. 5, and Plate 20% Figs. 13, 14). Tova has been well surveyed 

 (Plate 20% Figs. 13, 14, and Plate 23% Fig. 5) ; unfortunately we were 



