observed it in especial abundance on the fringing coral reefs surrounding what are known as M and N 

 Islands, belonging to the Northumberland Group, eastward of Mackay. This oyster is also to be seen in 

 some quantities tn situ, but no longer alive, on the dead and apparently raised coral reef on the west 

 side of Blagnetic Island, facing Townsvillo. As an edible variety the coxcomb oyster is somewhat large 

 and coarse, and is consequently mo.t appreciated in a cooked condition. A smaller variety of coxcomb 

 oyster is not unfrequently obtained from deeper water in Torres btraits attached to the branches ot the 

 black coral, Anfipafhes, and other zoophytes. It is remarkable for its production of finger-like projections 

 from the back of the attached valve. With the aid of these ])rojections it retains a secure grasp on its 

 chosen fulcrum, though at the same time this hold may be so loose that the shell may be slipped to and 

 fro on its supporting b.ase. This variety of oyster would appear to be identical with the Ostrcajolium ot 

 Linnaeus originally reported from the Indian Ocean. _ 



The second largest species of edible Queensland oyster is also an essentially marine type, ana 

 limited in its distribution to the tropical districts. It varies considerably in form, and may be either simply 

 ovate with/a broa«ler distal margin or boat-shaped with pointed ends, as, shown in the several figures ot 

 Plates IIJ. and lY., illustrative of this type. The larger individual shells of this species not unfrequently 

 measure as much as G 6i 7 inches in their longest diameter. Its edges, in contradistinction to the 

 precedino- spocies, are usually perfectly even, or only slightly indented. A notable feature of this oyster 

 is the very hard vitreous texture of its shell. Its colour externally is usually a light slate-grey, and, 

 interiorily, a pure white with a very conspicuous broad black baud throughout its marginal border. 

 In association with this last-named feature it has received the name of the black-edged oyster, Ostrea 

 nigro-marginatii. "While by no means an unpalatable oyster in the raw condition, it, like the preceding 

 species, finds greater favour in a stew or scallop. The black-edged oyster flourishes side by side with the 

 form next noticed, Ostrea worr/oj,-, throughout the reefs and islands of the Great Barrier systeai, and 

 is particularly large and abundant on the rocky foreshores of Adolphus and other islands in the vicinity 

 of the Albany Pass, Torres Straits, and from \vhence it is extensively obtained as a seasonable delicacy 

 for the settlement at Somerset. The hardness of the shells of this species, and the difiiculty ot' detaching 

 it from the rocks without fracture, even with the aid of hammer and cold-chisel, preclude its utilisation for 

 commercial purposes in the ordinary manner, though from its size and abundance in many localities it 

 might, in common with the form next described, be profitably canned or otherwise preserved. In 

 illustration of the substantial dimensions to which this oyster attains, it maybe mentioned that the 

 hollow shell, illustrated by Plate IV., Fig. 1, was found to have a holding capacity of four fluid ounces 

 or one-quarter of a pound of oyster meat. 



The third species of edible oyster, other than the ordinary' commercial type, indigenous to Queens- 

 land is the so-called Ostrea mordnx, of Gould. Its area of distribution is a much wider one than that of 



While enjoying so extensive an area of distribution, Ostrea mordax may be said to attain to its 

 finest or maximum development among the coral reefs and islets of the tropical coast-line of eastern 

 Australia, and from its remarkable abundance in this region it may be appropriately, and is hereafter 

 distinguished by the suggestive popular title of the Coral Rock Oyster. In contradistinction to the 

 ordinary rock ovster of commerce, this Coral Eock species is an essentially marine type, attaining to its 

 most luxuriant growth among the reefs and islets of the Great Barrier system, far remote from fresh water 

 influences, and rarely overstepping ihe boundary limit of pure salt water in its area of distribution along the 

 rocky headlands on the mainland seaboard. In this latter situation it not unfrequently grows as abundantly 

 and under conditions closely simulating those represented in the typical illustration given at Plate VII., 

 Fig. 1, of the rock variety of growth of Ostrea fjlomeruta. The zone of growth most affected by Ostrea 

 mordax on either the natural rocks, upheaved reefs, or stranded coral boulders, is coincident with that of 

 half-tide mark, and I have not so far, by either practical investigation or inquiry, obtained information 

 concerning any instance in which this oyster has been found growing beneath, or even "at as low, a level 

 as ordinary low-tide mark. 



The characteristic features of Ostrea mordax, in its most typical form, are its normally elongate 

 triangular contour, the very evenly lobatc edges of the interlocking shells, and the opaque purpli.sh-pink 

 hue of their external surface. Another peculiarity of this species as compared with the ordinary 

 commercial oyster, O. qJomeraio, which it often closely resembles in size and shape, is the circum- 

 stance that it is almost always affixed to its rocky support by its left valve, while the last-named form 

 is as invariably affixed by its right one The flattened, freely movable so-called opercular valve is in a 

 corresponding manner developed on the right side in Ostrea mordax, and on the left one in O. 

 glomerata. An additional point of distinction between the shells of these two species is furnished by 

 the circumstance that the scar or impression of the attachment of the large adductor muscle in O. 

 mordax is set very much further back, or towards the distal or growing edges of the shells, than obtains 

 in O. glomerata ; this scar, moreover, in the opercular valve is more usuallv of a deep-black hue, 

 while in the last-named species, though occasionally of a darker tint than the surrounding nacre, it is 

 more often colourless. 



While the shape as above described represents the most typical form of Ostrea mordax, it is 

 subject to almost as considerable a latitude of variation as the ordinary commercial oyster, O. glomerata. 

 This variation is the effect of its efforts to adapt its shape to that of its environment, and the .shells may 

 vary in consequence from an almost circular to an abnormally elongate contour. A yet more conspicuous 

 modification of the very variable species is one in which the hinge or butt-end of the attached valve is 

 produced into a long hollow beak, which is found, on opening the oyster, to contain a very considerable 

 amount of meat. This beaked variety would appear to be identical with tlic form upon which the specific 

 title of Ostrea cucuUata was originally conferred. Illustrations of this beaked variety, and also of the 

 normal form of Ostrea mordax, are given at Plate 11., Figs. 1 to 4. A characteristic feature of the 

 species under notice, so far unreferred to, is the one which, notwithstanding its excellent edible qualities 

 disqualifies it from occupying a place in the leading niar!<cts beside the more familiar commercial varieties. 

 This (lis(]ualit'ying feature is represented by the tenacity and cxtensiveness of its union to its rocky support, 

 and which is almost invariably coincident with the entire external superficies of the adherent shells. As 

 a neccs;:ary conscqucuco much labour is requisite to separate them from their attachment, and in the 



operation 



