BY H. I. JENSEN, D.SC. 191 



Mr. C. Hedley and others are carrying on similar work 

 ^th regard to zoological distribution. Mr. Hedley main- 

 tains that in the Middle Tertiary, when a wide peneplain 

 I -covered Eastern Australia and a lacustrine region occupied 

 j the interior, the giant marsupials, known from our newer 

 leads and bone beds, roamed far and wide, and fed on the 

 plenteous herbage produced by the moist climate. 



The elevation of the tablelands decimated them, for 

 the lacustrine interior became an arid plain on which 

 they died out of starvation, the table lands were too cold 

 and did not produce the proper herbage for these huge 

 animals. The great basaltic extravasation caused further 

 destruction to them, and the surviving remnant was 

 slaughtered by the blacks. 



An interesting effect of the basaltic outpourings on 

 the temperate tablelands of Eastern Australia was the 

 destruction of the Eucalyptus flora, and the failure of that 

 iiora to reassert itself. In coastal regions, basalt country 

 in the state of nature soon becomes covered with scrub, 

 as we call tropical moist climate jungles. Given good soil, 

 this flora can hold its own against the hardy typical 

 Australian flora. But on the tablelands the climate is 

 too dry and cool for tropical jungle ; and inland the climate 

 is also too dry and extreme, so that basalt flows in these 

 regions never become scrub covered. [35] The basalt 

 lands therefore remain treeless plains, for the Eucalyptus 

 and Acacia groups requires a loose loamy soil, but our 

 basalt soils are heavy, and shrink on drying. The cracking 

 of basalt soils may be the cause of a normal tree growth 

 failing to assert itself, and young trees having their roots 

 torn by the cracking of the soil. Again, it is possible 

 that the black colour and high lime content of black soil 

 may have some inhibitory effect on the germination of 

 seeds of plants typical of poorer country. This latter 

 problem has never been investigated. 



Some of the Tertiary changes of geography of 

 Australia must have been witnessed by the aborigines. 



In Victoria, and in the Mount Gambier district of 

 South Australia, basaltic volcanoes w^ere in active eruption 

 when the Australian aborigines and their dingoes were in 

 possession. 



