108 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
all sizes of the metamorphic rock forming the island. These pebbles 
are cemented with fragments of the rock oysters! which must once 
have grown upon the disintegrated faces, as they do now upon the faces 
of the rocks near low-water.mark. The flat (Plate IL) exposed by the 
tide is slightly raised along the northern and southern edges, and partly 
surrounds a shallow pool which is covered with dead corals and masses 
of the conglomerate from the elevated reef rock, which must have 
extended fully three hundred yards from the shore, and been eroded to 
form the face of the slope of the existing reef. The dead coral which 
covers the reef flat is undoubtedly derived from the breaking up of the 
coarse elevated coral conglomerate, of which only here and there very 
large fragments are met with on the flat exposed at low water. 
Associated with the granitic pebbles, and cemented with them in 
one solid mass, are found numerous fragments of many species of 
corals, mainly Madrepores however, which must have been thrown up 
when the elevated reef was flourishing, much as to-day we find the 
fragments of corals thrown up on high banks beyond high-water mark. 
Such a pile of fragments of corals from the southeast end of Middle 
Island flats (Plate ITI.) has been photographed by Mr. Woodworth, 
This peculiar conglomerate reminds me very much of a similar con- 
glomerate found in small patches at the base of Diamond Head (Oahu 
Island), a few miles from Honolulu. It is the same kind of conglomer- 
ate as that seen by Jukes at Cape Upstart and elsewhere on the east 
coast of Queensland, and which he mentions as evidence of a very 
moderate elevation of this part of Australia.? The old coral sand beach 
1 Kent has figured the Mangrove oysters from the estuary of the Endeavour 
River, near Cooktown, on Plate XXXIX., and on the same Plate also he has rep- 
resented the solid reef-like masses of Ostrea conglomerata, which occur in Keppel 
Bay and in Moreton Bay. While at Middle Island, and many other places on the 
islands near the mainland, we came upon the incrusting and most characteristic 
coral rock oyster, Ostrea mordax, which flourishes in pure sea water, and has been 
so well figured by Kent on Plate XL. 
2 Jukes (Voyage of the “Fly,” p. 335) writes as follows regarding the evidence 
of a moderate elevation of the northeastern part of Australia: — 
“T wish to refer to the masses of coral conglomerate forming strips of flat land 
along shore behind the present beaches, and to the presence of pumice pebbles 
sometimes in that conglomerate, but more usually scattered over its surface loose 
upon the ground. . . . The coral conglomerate has been already described, espe- 
cially that at Cape Upstart, and in the Capricorn group of islands. Flats composed 
of it, half a mile in width, are frequent along the shore of the northeast coast of 
Australia. It must either have been formed under water, in which case its exist- 
ence as dry land proves elevation of the whole coast, or it must have been produced 
