PEEFACE. 



As the publications of a Geological Survey cannot properly be 

 limited to the maps and sections, but would be incomplete without 

 figures and descriptions of the fossil organic remains made use of 

 for the determination of the geological ages of the different geolo- 

 gical formations of the country,* it has been determined to issue a 

 " Prodromus " or preliminary publication of the Victorian Organic 

 Remains in Decades, or numbers, of ten plates each, with corre- 

 sponding letterpress, on the plan of the Decades of the Geological 

 Survey of England, followed by the Geological Surveys of Canada, 

 India, and several other Governments. 



The Decades will contain figvires and descriptions in the first 

 place of the more characteristic fossils of each formation, of which 

 good specimens may be in the National Collection ; so that observers 

 in the field may make use of them for preliminary or approximate 

 determination of the geological ages of the strata they may meet. 

 A portion of the impression of the plates will be kept back until a 

 complete systematic treatise on the fossils of each formation may 

 be issued when the materials approach completion. 



In this fourth Decade the first three plates illustrate new species 

 of the gigantic elephantine marsupial forerunners of the little 

 Phascolarctos, or " native bears " of our own time, species of Dipro' 



* " Palseontological researches forming so essential a part of geological investigations, such 

 as those now in progress by the Geological Survey of the United Kingdom, the accompanying 

 plates and descriptions of British fossils have been prepared as part of the Geological Memoirs. 

 They constitute a needful portion of the publications of the Geological Survey." — Sir Henry 

 T. De la Beche, Director-General of the Geological Survey of the United Kingdom^ in notice 

 prefixed to the first of the Decades of the English Geological Survey, 



[ 3] 



