96 bulletin: museum of comparative zoology. 



towards the south off the -nest coast, and on the eastern face of the 

 island it attains a width of nearly a mile. In continuation of the 

 fringing reef off the northern face and off the southern spit of Lakemba 

 extends a naiTow outer reef, enclosing a lagoon, irregularly rectangular 

 in shape, about five miles in length. The lagoon is thickly studded 

 with patches and heads; its greatest depth is 14 fathoms; on the east 

 face of the outer reef there is a passage for steamers. This is another 

 exception of a lagoon entrance on the windward side. It should, how- 

 ever, be noted that the east face of the Lakemba atoll is protected to 

 some extent by Aiwa and Oneata. 



The resemblance in shape of Lakemba and Kanathea, the latter of 

 which we did not visit, is very marked. The encircling reef of the latter 

 surounds a larger lagoon ; there is also a naiTow extension of the lagoon 

 on the south side of Kanathea, and a boat passage on the east face. 

 One mile and a half south of Kanathea, and sepai'ated from it by a 

 channel with a depth of 131 fathoms, lies the small summit of Morse 

 Reef ; and off the central part of the northern face of the encircling 

 reef, Boehm Rock. At Lakemba Gardiner ^ has noticed the flat lime- 

 stone hills which rise abruptly to a height of 60 to 70 feet on the west 

 coast, the foundation being volcanic conglomerate, which forms the rest 

 of the island. Captain Wilson states that on the reefs of the extreme 

 south some of the islets are limestone, others volcanic, and he considers 

 the three larger islands in the centre to be the renmants of an old 

 crater. 



Thithia. 



Plate 30. 



I am informed by Bishop Yidal of Levuka that the island of Thithia, 

 which we did not visit, is also composed in part of elevated limestone, 

 in which larfre caverns have been excavated similar to those we saw in 

 Ngillangillah Island. It is also stated by others to be in part volcanic. 

 It resembles Mango in outline, appearance, and structure, but is some- 

 what smaller; the fringing reef surrounding it is narrow. The central 

 part of the island is probably a volcanic ridge, which has elevated the 

 ancient limestone surrounding it. 



1 Loc. cit., p. 466. 



