PHOTOTYPE PLATES NOS. XXXIX. AND XL. 6i 



reference to the locality in which it was first discovered — -the estuary ot the Ord Riven 

 Cambridge Gulf, in association with the surveying cruise of H.M.S. Myrmidon — the author has 

 conferred upon it the title of Ostira ordcnsis.* Concerning the illustration of the oyster-encrusted 

 Rhizophora-roots in Plate XXXIX., it remains to be recorded that this scene is taken from the 

 estuary of the Endeavour River, in the neighbourhood of Cooktown. It frequently happens that 

 the mangrove roots are encrusted with oysters very much more densely than is here shown. 

 Unfortunately, the author was not armed with his camera when exploring such more prolific 

 mangrove thickets. 



PLATE XL. 



(]l.)-OYSTER-REEF, KEPPEL BAY. 



A third and very distinct condition of the ordinary Australian rock o^'Ster, Ostira 

 glomcrafn, is aff'orded by this picture. In this instance the molluscs form a solid reef- 

 like mass, several feet in thickness, and of indefinite extent. The considerable portion 

 that has been undermined and broken up by the tidal currents displays the dense aggregation 

 of the oysters with remarkable distinctness. This prolific oyster-reef, in common with the 

 mangrove oyster-bank in the preceding plate, belongs to the Keppel Bay, or Rockhampton, 

 district, representing an area in the shallow, mangrove-bounded, channel known as the 

 " Narrows," which unites Keppel Bay with Port Curtis. This oyster-reef, as here portrayed, 

 represents the condition presented at extreme low tide, the whole of it is completely 

 covered at about half-tide level. Oyster-reefs of similar extent and thickness were formerly 

 plentiful in Moreton Bay ; but they have, for the most part, been broken up and utilised 

 as " brood ware " by the oyster cultivators. When massed together under natural conditions, 

 these reef oysters remain permanently dwarfed, whereas on being broken apart, and distributed 

 over the cultivation banks, they speedily grow to marketable shape and size. 



(B,)-C0R]1L-R0CK OYSTERS. 



The species of oyster that thickly encrusts the rocks in this illustration, is altogether dis- 

 tinct from the one depicted in the preceding views. While that type, the ordinary Australian 

 commercial rock oyster, is invariably found where there is either permanently or periodically 

 a considerable admixture of fresh water, the present form, technically distinguished by the 



* "Oysters and Oyster Cultivation at the Antipodes." By W. Saville-Kent, F.L.S. Communicated to the 

 Wellington New Zealand Meeting of the .\ustralian Association for the .Vdvancement of Science. January, 1890. 



