312 THE GREAT BARRIER REEF 



which have taken to a marine life. The limpets and sea- 

 snails come still closer to terrestrial species of molluscs ; 

 and many of the lowest forms of ocean life seem to be 

 derived from distantly related land animals of a similar 

 class. This is very noticeable in some of the lower forms ; 

 though I am constrained to remark that there are many 

 marine creatures which do not seem to have a parallel on 

 dry land, especially in the higher, or vertebrate, classes. 

 I cannot, however, enlarge on this curious subject here ; 

 but much remains to be said in favour of the theory that 

 marine classes have been evolved from terrestrial classes. 



The reef, of course, abounds with molluscs. So 

 numerous are the species that I cannot attempt to cope 

 with them within the bounds of a couple of paragraphs. 

 The pearl oyster {Meleagrina margaritiferd) is found in 

 large or small numbers in many parts of the reef; but it is 

 in the north and in Torres Strait that the greatest numbers 

 are found. Should the supply of shells in those districts 

 run short, probably a sufficient quantity of them would be 

 found as far south as the reef extends, to make the 

 fishery payable. 



Gasteropod shells of the Conus family are found on some 

 parts of the reef, one particularly fine one being of a bluish- 

 grey colour, with very beautiful violet veinings. Probably 

 some very rare and fine specimens could be procured here. 

 Certain it is that I procured several which were hitherto 

 unknown to our local collection, and were eagerly sought 

 after by the colonial museums ; and others I saw which 

 seem to be without representative specimens in European 

 collections. The spider-shells {Pteroceras) have several 

 representatives on the reef, the most remarkable being one 

 similar to the Swan River spider-shell, but double the 

 size of that variety. 



Of the numerous creatures of the lowest forms, number- 

 ing doubtless tens of thousands of species, which swarm on 

 all parts of the Barrier to the lowest depth I have 

 ventured to search, it is obvious I can give but the scantiest 

 of notice. Apart from the fact that these creatures could 

 not be adequately described except in technical terms, 



