30 BULLETIN : MUSEUM OF COMPAEATIVE ZOOLOGY. 



Murray,^ who visited Kandavu in the " Challenger," considers the 

 banks of Fiji surrounding the extremities of volcanic islands as banks 

 formed from the loose material of the islands spread out laterally by 

 wave action, the extensive banks extending much fai*ther seaward 

 there in one direction than in another. Murray has also called attention 

 to the North Astrolabe Reef, which, if its present condition with Solo 

 Rock in the centre is due to subsidence, should have a very much deeper 

 lagoon, instead of the comparatively shallow one characterizing that 

 reef. 



Great Astrolabe Reef. 



Plates 11, 11*, Figs. 10-13, and Plates 51, 52. 



To the northwai'd of the eastern extremity of Kandavu (Plate 11) ex- 

 tends the Great Astrolabe Reef. Its eastern face is the extension of 

 the reef to the eastward of Tomba ni Soso (Plate 10), an irregularly 

 shaped bay, the mouth of which is protected by a barrier reef. This 

 barrier reef extends as a fringing reef along the southern coast as far 

 as Kandavu Bay, where it becomes sepai-ated from the island and forms 

 stretches of barrier reef patches, with passages leading into the bays 

 protected by the reef. 



West of the entrance to Xgoala Harbor a broad fringing reef extends 

 along the southern coast nearly to the western spit of Kandavu. Sev- 

 eral reef harbors are cut out from it, one of which, Tomba Yauravu, is of 

 considerable size (Plate 10). From Xaingoro Pass the outer reef of the 

 ' Great Astrolabe Reef runs unbroken in a noi'therly direction for a dis- 

 tance of 2.5 miles round its northern horn, as far as Usborne Pass, which 

 is an entrance into the lagoon on the western side, aliout a mile from the 

 apex of the Great Astrolabe Reef. Off Mbulia, the easternmost of the 

 islands inside the Great Astrolabe Reef, the eastern encircling reef 

 makes a sharp elbow, and then forms a double curve in a northwesterly 

 direction to the narrow apex, from which the reef turns sharply south 

 as far as Alacrity Rocks in a great narrow arc broken in many places. 

 North of Ono Island there are three well defined passages, but south of 

 Alacrity Pass the reef becomes much broken up into small patches, 

 and finally, from Ono Island south the lagoon is open, and has a steep 

 slope towards the 100 fathom line. 



The depth of the lagoon north of Ono is not more than twenty-two 

 fathoms ; the bottom is most uneven, often passing rapidly from five 



1 Nature, July 4, 1889, p. 222. 



