22 RECORDS OF THE AUSTRALIAN MUSEUM. 



much more opaque and vitreous-looking appearance than that 

 seen in the other MoUusca. In one small guard in particular, 

 now before me, remains of the radiating fibres and concentric 

 layers of calcite are visible round the periphery, gradually fading 

 off into a dark blue and purple vitreous-looking opal. 



Pre-eminent for its beauty is a bivalve, obligingly lent to the 

 Geological Survey of N. S. Wales for examination by Mr. H. 

 Newman, jeweller, of Melbourne. This is without exception one 

 of the most beautiful conditions of fossilisation I ever beheld — 

 perfectly clear of the matrix, with the valves in apposition, and 

 save for a slight crushing about the centre of one of them, quite 

 perfect, wholly converted into Precious Opal, and with a play of 

 colour quite equal to the fragments in quartzite shortly to be 

 referred to. The shell substance is almost glassy transparent. 

 It is probably identical with the shell already referred to, with 

 the translucent fractured edges, from the collection of Mr. G. de 

 V. Gipps, also lent to the Geological Survey. 



Mr. J. E. Carne informs me that the Survey Collection con- 

 tained, previous to the Garden Palace fire, an Ammonite, wholly 

 converted into Precious Opal, six inches in diameter ! This came 

 from White Cliffs, and was probably one of the first fossils ever 

 obtained there. 



By no means the least interesting specimen found in this field, 

 previous to Messrs. Tweedie and Wollaston's reptile, is the half, 

 split longitudinally, of a Sauropterygian vertebra, with the 

 osseous matter converted in the first instance into the common 

 white and opaque opal, and the canals and lacunee remaining 

 open and filled with a little ferruginous powder. The roughened 

 edges of the fractured surfaces are then tipped, and the cavities 

 to some extent lined with Precious Opal. This is also from the 

 cabinet of Mr. J. de V. Gipps. 



Some polished hand specimens of a highly fossiliferous chocolate- 

 brown quartzite were presented by an unknown donor to the 

 Geological Survey Collection, the whole of the organic remains 

 being converted into Precious Opal, and the interstices between 

 the component constituents of the rock likewise similarly filled 

 as a secondary infiltration, probably replacing the calcite particles 

 of the deposit. Beyond the fact that these specimens come from 

 White Cliffs, I am not in possession of information as to the 

 stratigraphical position of this quartzite, but possibly it may be 

 derived from the water-worn vitreous boulders mentioned by Mr. 

 Jaquet as occurring in the clay and conglomerate beds. The 

 organic remains are those of MoUusca, with traces of Corals and 

 stem-joints of Crinoids, showing such a marvellous kaleidoscopic 

 play of colours that words are quite lacking to render the general 

 appearance of the specimens appreciable. 



