NOTES ON THE DISCOVERY OF A NEW FOSSIL 



FRUIT FROM THE DEET»-LEAD TIN DRIFTS AT 



DERBY, TASMANIA. 



By R. M. Johnston, I.S.O., F.S.S. 

 [Received 4th March, 1918. Read 11th March, 1918.] 



On my last visit to the Briseis Mine workings, at 

 Derby, the mining manager, Mr. Lindesay Clark, kindly 

 guided me over tiie various alluvial tin-bearing sections 

 now being sluiced by powerful hydraulic force. 



The formation in which the fine alluvial occurs at sue 

 cessive levels consists of white clayey seuinients of an 

 ancient lake-like river-coiurse, generally overlaid by a thick 

 layer of olivine-basalt. 



Among the successive alluvial tin-bearing layers of the 

 60 to 70 feet of clays, underlying the basalt, lenticular 

 patches of lignite frequently occur, where, as in the ligne>- 

 Oius clays of the auriferoius deep-leads of Beaconsfield, they 

 are assoeiated with fossil leaves, twigs, and fruits, now 

 regarded by me as of Eocene age, and contemporaneous 

 witn the fossil vegetable remains found abundantly inter- 

 mixed with the marine fossils of the Eocene age at Table 

 Cape. 



On the basis of the percentage proportion of extinct 

 to living forms the marine beds at Table Cape are now 

 generally assigned to the earliest Eocene period. 



I have always been confident that if the lignites of 

 the Briseis deep-leads were carefully examined after sluic- 

 ing operations, that fossil fruits would be found. The 

 discovery of such fruits woiuld then enaole us to determine, 

 with ooaifidence, the true relation of these older alluvial 

 tin-drift deposits to similar lignitic clays of the same char- 

 acter, underlying the older olivine basalts, in areas occu- 

 pied by the sediments of the numerous old Tertiary lake 

 basins, as at Macquarie Harbour, Mount Bischoff, "old 

 lake of the Derwent,' Launceston Xerti^i'y lake basin, and 

 elsewhere. 



The recent discovery, by Mr. Lindesay Clark, of a 

 large lignified fossil fruit (closely resembling and possibly 

 allied to Plesiocapparis prisca, F. von Mueller — occurring 

 in probably the lowest layers of the oldest auriferous deep- 



