212 SPENCER MOORE [sept. 1899 



range, lie tells us, which is of granite, is capped by conglomerates 

 doubtfully referred by Mr. F. T. Gregory to the Devonian age, but, 

 perhaps, as suggested by Mr. Etheridge, really Mesozoic. Since Upper 

 Devonian times there have always been land surfaces, at any rate in 

 Eastern Australia, where there was partial interruption to absolute 

 continuity daring deposition of the Carboniferous rocks. The country 

 presented the aspect of a vast archipelago while the extensive marine 

 cretaceous beds occupying the low -level tracts of the interior were 

 being deposited ; and not until the close of the Cretaceous period was 

 the continent formed. These marine beds — the so-called Rolling 

 Downs formation, of Lower Cretaceous age — w T ere laid down in a com- 

 paratively narrow sea connecting the Gulf of Carpentaria with the 

 Great Australian Bight, and there is no evidence for the existence of 

 interoceanic connection since that age, that is to say for the tertiary 

 sea of Professor Duncan and Mr. Wallace. Following close upon the 

 end of the Cretaceous epoch was another submergence during deposition 

 of the older tertiary strata ; but this did not involve so large an area, 

 as these marine tertiary beds are not found more than fifty miles inland 

 except round the Great Australian Bight and in the Murray Desert. 

 After this, by unequal movements of depression, Central Australia 

 became a lacustrine area, for the low-level deposits of this region are 

 of lacustrine origin as their remains prove. Lacustrine conditions 

 continued into Pliocene times, unless the formation known as the 

 desert sandstone, which is of Pliocene age, be eolian, as Mr. Tenison- 

 Woods conceives. The extinct rivers, the circumscribed lacustrine 

 basins marked by their coincident sand-beaches, and the remains of 

 large herbivores prove the climate of Central Australia to have been, up 

 till comparatively recent times, much moister than it is to-day. The 

 subsequent history of the district has been one of gradually increasing- 

 desiccation. 



(To be continued.) 



