and is also domiDant among those growing on the mangroves in the Endeavour River, near Cooktown. 

 It never attains to the large size of its southern congener, a shell having the capacity of a single fluid 

 ounce being of abnormal dimensions. This modified form would appear to be indentical with the type 

 upon whit^h, on insufficient evidence, the so-called Ostrea mytiloides, of Lamarck, has been established. That 

 it is a variety only, however, of the common species, and not a distinct form, is abundantly shown by the fact 

 that oysters approaching the normal triangular outline occur among them, while the orbicular variation, 

 on the other hand, may not unfrequently be detected growing among the typical triangular southern race. 

 Representative illustrations of this characteristic orbicular variety will be found at Plate I., Figs. 6 and 

 7. Within the circle covered by the ordinary triangular, the orbicular, and the abnormally elongate 

 modifications of Ostrea qlomerata that have now been enumerated, the inclusiou of any of the numerous 

 intermediate local variations that occur will be an easy task. 



COLLECTIVE CONDITIONS OF GROWTH. 



Among the several natural phases of growth under which the commercial oysters of Queensland 

 occur in marketable quantity and condition, that in which the bivalve spreads itself over extensive level 

 banks that are more or less uncovered at low water represents the most important. These" bank oysters" 

 may be attached to stones or dead oyster shells known as cultch, or, as still more frequently happens, to 

 the living shells of a peculiar species of whelk, Potamidcs elenimis, Bbug., whose name, with the 

 aborigines of Moreton Bay, is that of "Toondah." This whelk, which grows to a length of three or four 

 inches, is essentially herbivorous, feeding on the Confervte, lower algoe, and other vegetable organisms 

 that abound on the mud flats so favourable to the growth of the oyster. The free-swimming oyster 

 embryos, or " spat" become attached in large numbers to the exposed dorsal surfaces of the whelk's shell, 

 and are carried about with it among the most luxuriant pasture grounds. Within a few months' time the 

 oysters have increased to such a size and weight that the whelk is no longer able to travel with its burden, 

 and where the ground is soft sinks into the mud and ])erishes, leaving the living crown of oysters to mark 

 the position of its interment. Of the number of oysters originally adhering to the whelk, some four or 

 five, representing the survival of the fittest, usually grow to maturity and marketable size. Included 

 among some very fine examples of whelk-oyster growth placed at my disposal by Dr Bancroft, I found that 

 the load of oysters carried by the living whelk frequently weighed as much or more than half-a-pound, 

 while the whelk itself barely weighed an ounce. 



A typical illustration of an oyster bank, representing one of the rich oyster grounds of the Bribie 

 Passage, Moreton Bay, is given at Plate V., Fig. 1. It is noteworthy that the banks in this district are 

 formed more exclusively of oysters attached to ironstone pebbles lying upon a substratum of gravel and 

 tenacious mud. They enjoy a high reputation for their shape, size, and flavour. Oyster banks of the 

 character described exist in the most luxuriant natural conditions throughout Moreton and Wide Bays, the 

 northernmost ])oint of their occurrence being Rodd Harbour and " Seven-Mile Creek," a little south of 

 Gladstone and Port Curtis. The oysters on these northern beds grow under conditions, on whelks or on 

 separate shell or stone bases, preciselv parallel with those of their southern congeners, but do not in that 

 higher latitude attain to so large a size. The experiment of transporting these smaller northern oysters 

 to southern banks is now under trial, with every promise of a successful issue, though the considerable 

 interval of, approximately, twelve months has apparently to elapse before the new growth commences 

 that is required to convert them to marketable dimensions. 



Concerning bank oysters generally, it may be mentioned here thac Ibis form of growth represents 

 the most important from a commercial standpoint. Not only are the largest numbers of oysters sent to 

 market taken from the banks, but it at the same time furnishes emplovment and a livelihood to a very 

 extensive section of the community. In this connection it may be affirmed that probably in no other 

 country in the world is so healthy, congenial, and unlaborious a means of earning a substantial competency 

 open to, and turned to practical account bv, all classes as that of bank ovster culture in the Queensland 

 oyster- producing districts of Moreton or Wide Bavs. With a nominal rental payable for the ground 

 cultivated and occupied for a homestead, a climate that permits of dispensing with all but the most 

 necessary form of raiment, and fish procurable in such abundance as to substantially minimise the 

 butcher's bill, no more perfect terrestrial elvsium is probably at the disposal of small capitalists having 

 sufficient means for the supply of their most immediate necessities during that first year or two that must 

 elapse before their oyster crops have increased to a remunerative extent. 



The description of growth ranking next in importance to the bank series constitute what are 

 known as oyster reefs. These in their most typical form consist of solid masses of oysters that may be 

 several feet in thickness, raised to a higher level than the banks — the tops being exposed at about one- 

 quarter ebb. As a rule, the upper crust, representing some five or six to twelve inches in thickness alone 

 of these reefs, consists of living oysters, the substratum being composed of the dead shells of their 

 ancestors. These reefs in their most characteristic state rest simply on a clay or gravel basis, but are not 

 unfrequently associated with a rocky outcrop as their starting point. Oyster reefs, while formerly 

 abounding in Moreton and Wide Bavs, are now represented in greatly diminished numbers. Their 

 constituent oysters, in consequence of their crowded growth, are of small dimensions, but on being broken 

 apart and distributed on the banks soon increase to a marketable size. Such reefs have consequently 

 formed one of the main sources for the collection of stock for cultivation on the banks, and this to such 

 an extent that few if any reefs are to be found in their pristine massive condition throughout the oyster 

 grounds of the Southern district. A highly characteristic illustration of a typical virgin oyster reef 

 selected from those which occur in the neighbourhood of "The Narrows," between Port Curtis and 

 Keppel Bay, is given at Plate V., Fig. 2. The oysters in this reef are accumulated in a solid mass four 

 or five feet thick, their density being well shown by the portion which has been undermined by the 

 current and broken away from the parent mass. The oricinally horizontal superficial area thereby 

 exposed serves also to illustrate the rounded or sub-orbicular shape previously^ alluded to, that usually 

 characterise the growth of oysters where massed together in this mere northern district. The basis of this 

 luxuriant oyster reef and of others in the same locality consists chiefly of gravel and coarse sand 

 overlaying a tenacious clay, larger pebbles or small drift boulders transported through the agency of 

 flood currents being here and there interspersed among the general mass. 



Typical rock oysters, wherein the bivalve occurs in masses attached to rocks, are well represented 

 in the illustration Plate Yil. Fig. 1, reproducing the rocky outcrop with attached oysters at Burleigh 

 Head, near the mouth of Tullebuggera Creek, a little to the south of Southport. The oysters growing 

 under these conditions, though smaller in size than the bankers, are often of a deep puppy shape and 



excellei}^ 



