160 BULLETIN OF THE 



preserved ; but in the continuation of the dividing ridge between the 

 valleys of Nuuanu and of the Manoa, they have been denuded on eagh 

 side of that ridge and appear again on the eastward at a few points 

 on Diamond Head and towards it on the west. But the lower levels 

 of the same reef can be traced continuously along the present south- 

 ern shore line all the way from Diamond Head. The salt ponds and 

 flats, which extend inland in the Manoa Valley between Honolulu and 

 Waikiki seem to indicate an inner lagoon much like that of Pearl River, 

 which has gradually been filled up by the silt swept down by the river. 



The comparative poverty of the fauna of the Honolulu reef is undoubt- 

 edly due to its being on the lee side of the island of Oahu, the outer face 

 of the reef alone obtaining a fair supply of food, brought by the westerly 

 current due to the trades, which runs along the south coast of Oahu. 



Mr. Rose was kind enough to take me out in a canoe to examine the 

 corals in Kaneohe Bay. We found the bottom of the bay covered in 

 many places by numerous more or less circular patches of living corals 

 (Plate V.) in all stages of growth, from domes a few feet below the level 

 of the sea covered by flourishing corals to small fringing reefs round the 

 shores of the islets and rocks which occur in the bay, and to elliptical 

 reefs, awash when the corals were living only on the outer slopes. The 

 bases of all these islands are undoubtedly summits of volcanic rocks 

 projecting above the general level of the bay, which have been coated 

 or sun-ounded by corals. To the southward of Kaneohe Head, on the 

 plain of Kailua, are extensive dunes similar to those already described. 



The edge of the bay is itself entirely surrounded by a fringing reef 

 (Plate V.) of corals, mainly of species of Porites, which have gradually 

 died out near the shore, and thrive only near the deeper water on the 

 edge of the channel. The opening of the bay is barred between Kapapa 

 and Ahuo Laka by a barrier reef (Plate V.) of very moderate thickness, 

 extending towards Kekepa and Mokolii, resting upon a lava bottom, 

 which is exposed in places. There are two entrances into the inner lagoon 

 of the bay. The breakers pound heavily upon this barrier, and from 

 it huge coral blocks ai-e constantly thrown up and ground to pieces, 

 the sand being carried in towards the bay and forming the bar of the 

 harbor. Dana looks upon these huge blocks, as well as the islands off 

 Kaneohe Bay, as having been elevated from six to eight feet above high 

 tide. 1 Kaneohe Bay is to a certain extent sheltered from the full force 

 of the trade winds by the small peninsula of elevated coral reef which 

 stretches to the eastward of the bay. On the barrier reef, as well as on 

 1 Dana, J. D., Geology of U. S. Exploring Expedition, p. 253. 



