58 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



crest of the highest ridge is flat, and runs at a general level of about 

 300 feet. The highest summit, toward the southern end of the island, 

 is nearly 400 feet ; off that point there are indications of a terrace at 

 about one third the height of the island, as if the elevation of this 

 group had taken place at two successive periods. Yangasa Levu seen 

 from the west, on the way to Ongea, appears hat-shaped, with a high 

 terrace forming the rim. The island of Yangasu Levu is from one to 

 two miles distant from the inner edge of the outer reef flat forming the 

 eastern horn of the lagoon. Along the western side of the lagoon are 



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~ii J i^-km 



TAXGASA LEVU. 



situated Navutuira, in the northwest angle of the lagoon, which rises to 

 270 feet; this is connected with the islet of Yuvutha (Plate 90) by a 

 long narrow reef studded with mushroom-shaped rocks rising above 

 high water mark. The whole of the northwestern part of the lagoon 

 to the west of the ship passage on the north face of the outer reef flat is 

 also thickly studded with negro-heads and with mushroom-shaped rocks 

 of all sizes and shapes, which cover the wide reef flat to the west and 

 north of Xavutuira. The large mushroom-shaped heads are generally 

 on the extension of spits or headlands of the two islands named. 



The crest of Navutuira is undulating, and from its shores rise low 

 undercut vertical blufi's. Yuvutha (Plate 90), on the contrary, has a 

 conical outline, its highest summit rising to 240 feet ; its vertical shore 

 bluff's are higher than those of Xavutuira, deeply undercut ; they are 

 nothing but the rim of a sound left from the disintegration, denudation, 

 and erosion of the adjoining land. Such rims are at a distance readily 

 mistaken for the rims of extinct craters. We anchored off" the west side 

 of Xavutuiloma, the most southern of the islands along the west side of 

 the lagoon. The small bay on the north face of Xavutuiloma resembles 

 closely a pai*t of the rim of an extinct crater. But that rim and those 

 forming the eastern and western points are entirely composed of ele- 

 vated limestone, full of caverns and caves, pits and potholes, many of 

 them full of red earth, as is the case wherever elevated limestone is 

 met with; it is deeply honeycombed and cut into ridges (Plate 92), 

 upon the edges of wliich rise endless sharp pinnacles and needles. 

 This was also the structure and appearance of the inland slope of 

 the island where we lauded. 



