0]-STERS AND OYSTER FISHERIES OF QUEENSLAND. 249 



Science, submitted to the author by Professor G. B. Howes, associated with the title of Osfrca 

 cornncopia', represent, apparently, abnormal growths of Ostrea edulis, while the more normally 

 elongate American species, Ostrea virginiana, produces numberless " sports " in a corresponding 

 direction. 



Among other subsidiary characters, which may be cited, as indicative of the close relationship 

 of the variety cornucopiaeformis to the ordinary Ostrea uiordax, is that of a similar peculiarly 

 opaque purplish-pink tint of the external surface of the shells, with which is combined a corre- 

 sponding striate sculpturing of microscopic fineness. The scar-like marking on the opercular 

 valve, due to the attachment of the adductor muscle, is also invariably of a black hue. The 

 associated clusters of this remarkable oyster, when viewed superficially, with little beside the 

 opercular shells visible, can in no way be distinguished from the ordinary growth of Ostrea mordax ; 

 and it is only on breaking them asunder and exposing the abnormally elongated lower valves that 

 their distinctness becomes apparent. The aspect and flavour of the " meat " of this oyster also 

 correspond with that of the ordinary mordax ; and of it, from within the deeply-excavated 

 lower valve, a much larger morsel is to be extracted than outward appearances at first sight 

 suggest. The localities on the Queensland coast, in addition to the vicinity of Keppel 

 Bay, where this variety cornucopiaeformis may be found, include the neighbourhood of Sweer's 

 Island in the Gulf of Carpentaria ; and animals modified in the same direction, but to a lesser 

 degree, have been collected by the author near the Bay Rock Lighthouse in the vicinity of 

 Townsville, and at Flat Top Island, off Mackay. The likeness borne by the shells of these 

 oysters, as illustrated in Chromo plate XIV., to the habitations of the Trap-door Spider, that 

 may be dug out of the soil of the adjacent mainland, is so highly suggestive, that the popular 

 title of "Trap-door Oysters" might be appropriately conferred upon them. 



A small species of oyster, tolerably abundant in various parts of Moreton Bay and fur- 

 ther north, which has in some instances encroached upon, and taken possession of, banks for- 

 merly occupied by the ordinary commercial species, is the Ostrea crenidifcra of Sowerby. This 

 variety is usually less than one-half the size of the commercial oyster ; and, while somewhat 

 resembling that in general shape, it may be distinguished from it by the more numerous, 

 acuminately pointed, denticulations of the peripheral border, which are continuous, as in O. 

 cristi-galli, with raised edges of the external surface of the shell and radiate from the hinge or 

 umbo to the periphery. Like Ostrea mordax, this species is usually attached by the left 

 valve. The colours of the shells of this small species are very distinct, being of a uniform 

 greyish-white externally and greenish within. While too small for commercial purposes, the 

 increase of Ostrea crennlifera on the banks should, as far as practicable, be kept down, as, 

 if left undisturbed, it will spread over the most favourable breeding and spatting grounds, and, 

 in addition, appropriate food material that would otherwise contribute to the nourishment 

 of the more valuable species. 



