BY E. C. ANDREWS. 537 



geological evidence, however, of a complete separation of West 

 from East. This is all the more remarkable, because the period 

 was one of great peneplanation, and a barrier to the junction of 

 the Indian and Southern Oceans, across Australia, by the trans- 

 gression of the Cretaceous Sea, is difficult to understand. 



The characteristic soil of Australia, during the Cretaceous, is 

 evidenced by the sandy and porous nature of the Cretaceous sedi- 

 ments. 



A study of Western and Eastern Australian geology suggests 

 that the surface of the continent was mostly sandy in nature, 

 although the various slate- and shale-deposits formed local excep- 

 tions. 



In the Lower Tertiary, the Cretaceous Sea was drained off the 

 continent in great measure, and the climate of the centre began to 

 change slowly, the old equable and genial conditions giving place 

 to greater extremes of heat and cold, and increasing desiccation. 

 The present stage of dryness over the whole central continent, 

 however, appears to be a recent development. 



In the Eocene, the Cretaceous Plain appears to have been 

 warped somewhat on its eastern margins, and in both this and a 

 later period of the Tertiary, deep leads were formed, and great 

 floods of basalt covered many portions of the lowlying eastern con- 

 tinent. During the great "Deep Lead" Period, the warped eastern 

 continent had been partly reduced again" to a peneplain. 



The Deep Leads contain infrequent traces of Eucalypts, but 

 not of other Myrtaceas, in fact the numerous plant-remains sug- 

 gest the occupation of Eastern Australia, during that period, by 

 Indian types,* although plants closely allied to Callitris and Bank- 

 sia are frequently found in the leads. , At the present day, the sur- 

 face of the areas, in which these remnants of tropical types have 

 been found in such abundance, is occupied mainly by cold-loving 

 types of Australian plants, owing to the formation of plateaus in 

 these areas. 



* Baron von Mueller, New Vegetable Fossils. Decades i.-ii., 1874-1882. 

 40 



