AGASSIZ : FIJI ISLANDS AND COKAL REEFS. 91 



flat as far as we followed it to Avea. The blufis forming the steep 

 sides of the island are undercut and deeply indented, forming gorges 

 and ravines (Plate 74) which cut into the island or separate dome-like 

 islets from the adjacent shores. The elevated limestone is full of species 

 of coral, mainly large heads of species of Astrteaus, of ^I*andrinas, and 

 Pocillopores, which appear to be closely allied if not identical with those 

 now living. One of the points of Ngillangillah was mei'ely a thin shell 

 covering a huge cavern some 50 feet hi diameter and rising to a height 

 of nearly 100 feet, and full of stalactites. The rock in the pool at its 

 base was covered with Gorgouiaus and small corals, and abounded in 

 Comatulse. 



The narrow channel lying between the north shore of the large island 

 and the outer reef is full of flourishing coral patches. The many nar- 

 row deep canons (Plate 74) cut into the face of the island with the 

 dome-shaped or mushroom-shaped heads of elevated reef rock projecting 

 a few feet above the water line give to this shore line a very picturesque 

 appearance. It is a simple matter to follow the extent of the elevated 

 reef rock eastward, and to trace the gradual appearance of the central 

 ridge of volcanic rocks until we come to the headland north of Koro 

 Mbasauga (Plate 72), where we find only a comparatively small outlier 

 of the elevated limestone, and a similar one to the south of tlie village. 

 Northeast of Koro Mbasanga lies the island of Avea (Plate 75), which 

 rises to a height of 600 feet, and which is wholly composed of elevated 

 limestone. This island as well as Susui runs at an angle from the 

 outer reef, and shows the great width of the former elevated reef. From 

 Koro Mbasanga south and for some distance beyond Lomaloma the vol- 

 canic rocks occupy the whole width of the island, and the elevated lime- 

 stone has disappeared to reappear again on the southern spit of the main 

 island, and to extend eastward in the islands of Malatta and of Susui 

 and their many outliers, as heads, rocks, and islets, both on the northern 

 and off the eastern point of the latter island. The island of Munia 

 consists, like the central part of Vanua Mbalavu, of volcanic rocks. The 

 island of Thikombia i lau, on the contrary, is composed of elevated lime- 

 stone rising to a height of 550 feet. Beyond Avea lie the Sovu Eocks, 

 three small islets about two miles inside the outer reef, also of elevated 

 limestone, one of which rises to a height of 230 feet. Between Avea 

 and the Sovu Islets runs southerly for a distance of nearly five miles a 

 series of narrow coral patches, which, so far as I can judge, are rem- 

 nants of the ancient elevated limestones, as are probably the heads and 

 patches of the eastern part of the lagoon beyond the Tongan Pass. Oa 



