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 1 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 II.) 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 III.) 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. 2 The old coral sand beach 



1 Kent has figured the Mangrove oysters from the estuary of the Endeavour 

 Eiver, 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 tlie 

 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 : — 



"I 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 



