92 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the contrary, many of the heads lying off the central parts of the east 
coast of Vanua Mbalavu are undoubtedly of volcanic origin, and are 
merely covered with a thin veneer of growing corals. Some of the small 
voleanic rocks and islets off the east central part of the east coast of 
Vanua Mbalavu are deeply undercut and eroded into mushroom-shape. 
By far the finest example of marine erosion of volcanic rocks is seen on 
Plate 62, which represents an eroded shore line with mushroom-shaped 
rocks off the shore, indicating a slight recent elevation. Plate 62 is 
taken from a photograph given us by Mr. E. G. Jones, and taken in Lau; 
unfortunately I am unable to state the exact locality. The islets of Yanu 
Yanu forming the harbor of Lomaloma consist of a yellow volcanic mud 
full of rounded pebbles, and some of the spits of the east coast of Vanua 
Mbalavu are composed of bedded volcanic mud (soapstone) similar to 
that found at Suva and its vicinity. The condition of the islands and 
islets and rocks, both of those composed of elevated coral reefs and of 
voleanic rock, clearly indicates the great denudation and erosion which 
VOLCANIC HILLS BACK OF LOMALOMA. 
have taken place, to leave only such fragmentary remains of the land 
which must have once occupied the area of the lagoon. It is possible 
that the age of the elevated limestone found at so many points in Fiji 
may be comparatively great, and that the ancient limestone forming the 
substructure of the reef of the present day may have been deposited in 
late tertiary times, immediately before the present epoch.’ 
As has been observed, the dip of the lagoon is to the eastward, or 
rather, in a general way, toward the slopes of the deep tongue of water 
forming the American Passage (Plate 19). This would seem to be the 
natural result of the elevation of the great flat of tertiary limestones 
1 See the report of Dr. Dall, referred to in another part of this Bulletin. 
