228 



PRELIMINARY OBSERVATIONS ON A NATURAL HISTORY 



only of the attached valve, and it is due to this circumstance that 

 the clusters or bunches can be readily separated for the market. 

 Yet a third feature— apparently hitherto unnoticed, which 

 appears to me to afford a subsidiary point of distinction between 

 the two species, is the circumstance that the adductor muscle r 

 with its accompanying shell-impressions, is set much further 

 back or towards the distal or growing edge of the shell in 

 0. mordax. as compared with that of 0. qlomerata. In the last 

 named species, it may be described as sub-central, while in Ostrea 

 mordax its location more frequently intersects a line drawn 

 transversely midway between the centre and the distal border. 

 With reference to the distribution of Ostrea mo^rinx, I may 

 mention here that it occurs abundantly throughout the ocean 

 coastline of eastern Queensland. Among the specimens- 

 now exhibited are some -tine examples placed at my disposal by 

 Mr. Hedley, and which were collected by him in the neighbour- 

 hoods of Soutbport and the Curumbin Heads, a few miles 

 distance only from the New South Wales border. 



Before leaving the subject of oyster?, I may incidentlv mention 

 here that the separate method of attachment that assies to dist- 

 tipfcnish Ost >■<>,( mordax from 0. qlomerata is an altogether unstable 

 character in Ostrea eduli*, and its varieties, as met with in the 

 Southern Colonies. Tn this species as demonstiated by quantities 

 artificially cultivated by me in Tasmania on slate and wood collectors, 

 the moHusk attaches itself indifferently by either shell. A similar 

 uncertainty as to the method of atiachment obtains also in the 

 diminutive species found growing on the leaves of the mangrove 

 trees in Cambridge Gulf. Respecting the many other so-called 

 species of Australian oysters, I am not in a position to say much at 

 present. The entire nomenclature of the genus Ostrea has unfortu- 

 nately got into great confusion owing to the lavish n duplication 

 of species, on the basis, in many instances, of the most trivial local 

 variations. The tendency of more modern writers has been to cut 

 the Gordian knot, by lumping them altogether again as varieties 

 only of a single species. A more careful and exhaustive investiga- 



