FISH AND FISHERIES. 111 
beds are always in moderately deep water, and never uncovered by the 
tide. It is the common oyster of New South Wales and Brisbane, and 
is largely exported to the neighbouring Colonies. 
It is commonly supposed, says Dr. Cox, that this species and the rock 
oyster are identical, and with this view many persons have gathered 
rock oysters-and planted them in beds with a view to their cultivation: 
He maintains, however, that this only leads to loss, for if this species’ is 
placed in positions where it is uncovered by every tide, it speedily dies ; 
but if properly cultivated on the beds it usually inhabits, it will become 
a most important article of food. 
Mr. Oliver and many others maintain that the drift oyster will 
flourish well if left under the same conditions as the rock oyster, that is 
where it is uncovered by every tide. The first-named gentleman tells 
me that he has tried the experiment, and succeeded in rearing a fine lot 
of drift oysters. On the other hand, rearing rock oysters in drift 
oyster beds is an experiment successfully and frequently effected by 
every oyster grower. Altogether the evidence preponderates in favour 
of the theory that 0. subtrigona and O. glomerata (that is the so-called 
rock and drift oysters) are the same species under different conditions. 
With ordinary care and attention they may be grown in deep or tidal 
waters. 
The Rock Oyster. 
O. glomerata, or Rock Oyster. This is the kind which is found so 
abundantly adhering to the rocks on all the east coast of Australia, Dr. 
Cox regards it as distinct from that which occurs so abundantly on the 
Queensland coast, especially on the coral reefs, where all the outstanding 
blocks of coral (nigger heads) are covered with them. This is Ostrea 
mordax, Gould. Having given the subject every consideration in 
travelling along the east coast I cannot regard the species as distinct. 
No definite specific distinction can be found when large numbers of species 
are examined. This oyster is generally found adhering to rocks which are 
not always covered by the tide. 1t is often beautifully frilled, and of a rich 
purplecolour. “Tf,” says-Dr. Cox, “ 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 attacks of a 
number of other molluscs, and unless the water which flows over them 
is pure, and free from decomposed vegetable matter and from grit, they 
suffer from the irritation caused by such particles, some discolour 
and waste-and others die.” To this species is also to be referred 0. 
cacullata of Born. The variety is merely an overgrown form of the 
hinge very common on the coral reefs. 
A Royal Commission was appointed in the latter end of the year 1876 
to take the important question of the Oyster Fisheries into consideration, 
and a very excellent Report from that Commission was brought up and 
