130 EDIBLE OrSTERS POUND ON THE AUSTRALIAN COAST, 



with thick concentric laminso ; lower valve cucullated, purple- 

 white within edged with purple or black ; lateral margins denticul, 

 ated ; hinge generally attenuated, produced, pointed." 



Having made a very careful examination of our common Eock 

 Oyster a,nd compared it with the description of this species and 

 that of others, I conclude that our Eock Oyster must be referred 

 to this species ; it is not Ostrea ciicullata. The only other species 

 which it could be referred to is the one which it was referred to 

 by Mr. G. F. Angas — Ostrea mordax of Gould. The latter is 

 acutely denticulated within between the lobes, and the border 

 between the denticles is of a deep purple brown ; these characters 

 are the most important and are not found in our common Rock 

 Oyster as they are in the Oyster adhering to the rocks on the 

 eastern shores of Queensland. 



I do not concur with Eeeve in looking upon Ostrea apinosa^ 

 Q/Uoy, as possibly a young of 0. glomerata or 0. cucullata ; the 

 young of these two species never approach that form. 



4. OsTREA MORDAX, Gould. 



This species is a Rock Oyster found adhering very firmly to 

 the rocks by the whole of the lower valve from Brisbane in Queens- 

 land to far North beyond Port Denison where probably it is found 

 in greatest perfection ; by consumers it is considered a great 

 luxury and of finer flavour than any of our Southern species, it 

 occupies a zone so as to be uncovered by the falling tide, which 

 is very great in those localities. 



The habitat of this species, is given doubtfully by Reeve as 

 California, but it is not found there. Mr. John Brazier found it 

 at Samoa, and at the Fiji Islands. It is also found at Port 

 Denison, Queensland, and probably all along the coast north of 

 Moreton Bay to Cape York, and at Lord Howe's Island, &c. 



It is a compressed shell deeply lobed at the margins, 

 between these lobes within it has acute denticles, and the border 



