BY J. C. COX, M.D., F.L.S. 129 



an error), and it is recorded by Hutton as the Rock Oyster 

 of Auckland, but not found further south in New Zealand. The 

 fact is this species has a very wide range, from King George's 

 Sound along the Great Australian Bight to South Australia, 

 thence all along the coasts of Victoria and New South Wales as 

 far north as the Tweed Eiver. 



This oyster occupies a zone above any of the other species 

 it is seldom found in the zone occupied by the Mud Oysters, 

 and certainly never in such deep water as that in which Ostrea 

 stihtrigona is found. Generally it is found adhering to the rocks 

 considerably above low water mark, and in places in the upper 

 Marine zone among the Trochocochlea and Nerita ; it varies 

 much in form and appearance, at times being beautifully and 

 delicately edged with a frill of a purple hue, at other times it is 

 large hooded and unfringed at the edge, the latter forms are 

 generally the best oysters. 



If individuals of this species are placed in proper trenches or 

 in positions where clear fresh sea water will flow over them at 

 each tide, they thrive and fatten to an extent which makes them 

 a valuable article of food, and an important commercial product ; 

 and by placing low stakes of wood or other material for the 

 spat to adhere to when emitted from the mother shell, they are 

 easily and successfully propagated; but when placed in such 

 positions, especially on mud-flats which are uncovered by every 

 tide, they are liable to the attack of a number of other Mollusks, 

 and unless the water which flows over them is pure and free 

 from decomposed vegetable matter and grit, they suffer from 

 irritation caused by such particles, some discolor and waste, 

 others die, and considerable loss may occur to the Cultivator 

 from causes which may or may not be within his control. 



The following is Eeeve's description of this species : — '' Shell 

 thick, irregular, sharp-ribbed with the margin dentated or lobed, 

 very inequivalve ; upper valve opercular, compressed, wrinkled 

 I 



