32 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
probably covered the greater part of the area now enclosed by the Great 
Astrolabe Reef. 
If we examine Kandavu Island itself (Plate 10), we can easily see 
how far denudation and erosion, if continued, would cut it up into a 
number of larger or smaller islands ; as, for instance, an island would be 
formed at the neck separating Tomba Kaivala from Koro Levu, a larger 
island, by the cutting of the neck separating Tomba ni Ndaku on the 
north side from Tomba ni Soso on the south of the island. Finally, the 
cutting of the Malatta Isthmus would make two islands of considerable 
size of the western half of Kandavu, while the many spits bounding the 
deep bays of the island would also become islands similar to Matanuku 
on the south side of Kandavu, and connected with it by the broad 
fringing reef. These would all be enclosed on the south by the southern 
extension of the Great Astrolabe Reef, which is now either a barrier or 
a fringing reef along the south coast of Kandavu, while on the north 
coast the island would merely be flanked by outlying reef patches sepa- 
rated by great stretches bare of reefs, as along the southwestern part of 
the Great Astrolabe Lagoon. 
Skirting the northern shore of Kandavu from Tomba Kaivala to 
Levuka, we found the physiognomy of the larger island to be identical 
with that of the islands of the Astrolabe Lagoon, — high cliffs, formed 
by the crumbling of the faces of the shores, sloping to high mountains, 
deep bays extending far inland, and a vegetation identical with that of 
the adjoining islands. According to the position and proximity of the 
islands to the inner edge of the outer reef flat, we found the bottom of 
the Great Astrolabe Lagoon to consist of volcanic mud or of coral sand 
and coralline algze, or of a mixture of the two. 
North Astrolabe Reef. 
Plates 11, 11°, Fig. 14, and Plates 53, 54. 
North Astrolabe Reef is separated from the northern point of the 
Great Astrolabe Reef by the D’Urville Channel, which is about a mile 
wide, and with 190 fathoms coralline bottom in the middle (Plate 11). 
North Astrolabe Reef encloses an oval egg-shaped lagoon about four 
miles in length by three and a half in breadth, with a small rocky islet, 
Solo, situated nearly in the centre of the lagoon (Plate 11). The great- 
est depth of the lagoon is sixteen fathoms, with very undulating bot- 
tom full of rocky and of coral patches along the inner edge of the reef, 
and especially over the southern part of the lagoon. Solo is composed 
lal et 
