ON THE INFLUENCE OF PHYSIOGRAPHIC CHANGES. 319 



Sandstone of North Australia, stretching across from the Victoria 

 River to the country south of tlie Gulf of Carpentaria, they wrap 

 round Lake Eyre on its east, south and west sides, extending 

 westerly so far as known to beyond Mt. Paisley in lat. 135". The 

 existeuce of this upraised Cretaceous bed, thoui,di probably of 

 inconsiderable elevation, implies during the period of its deposition 

 the submergence of a large extent of country. The Autochthonian 

 Region would be reduced to the condition of an archipelago widely 

 separated from another chain of islands in what is now the 

 meridianal elevation in South Australia, whilst a larger body of 

 dry land existed on the east coinciding with the Cordilleras of the 

 Euronotian Region. 



Secondly. — Following close on the extinction of the Cretaceous 

 Epoch was another submergence during the deposition of our Old 

 Tertiary beds, but which did not involve so large an area as the 

 former one, inasmuch as the general elevation above sea level of 

 marine beds of this age is only about three hundred feet, and 

 their extension inland does not exceed tifty miles, except around 

 the Great Australian Bight, and in the Murray Desert. During 

 this period of submergence much of the Eremian Region must 

 have been dry land, and may have afforded a way of intercommuni- 

 cation between the floras on either side, but not so, if present 

 climatic conditions were as actively repellant then as now ; of 

 this we have not actual evidence though it may be reasonably 

 deduced from the facts bearing on oscillations of climate that it 

 may so have been. 



Professor Martin Duncan* and Mr. Alfred Wallacef have each 

 assumed that the Old Tertiary sea extended in a wide gulf from 

 north to south through Central Australia. I know not on what 

 foundation these authors had based their assumption ; possibly 

 Mr. Brough Smyth's Geological Map of Australia may have been 

 to them a Will-o'-the-Wisp, as the Tertiary rocks are indicated on 

 it by one colour only. Now the beds of this pei'iod which cover 

 an extensive area in the medial portion of Australia are of 

 lacustrine origin and belong to a comparatively modern epoch. 



Whether or not the circumstance that several maritime species 

 re-appear in the Eremian Region, and which count among some of 

 its most characteristic plants, had influenced the forenamed specu- 

 lative minds I cannot say ; that it has not escaped the notice of 

 local observers is well known, who are to some extent answerable 

 for the propagation of a popular fallacy that the lake region of 

 Central Australia has recently been cut ofl" from Oceanic waters. 



The maritime plants are Lepidium ruderale, Nitraria Schoheri, 

 Frankenia Icevis, Plumbago zeylanica, Sctlsola Kali, Mesembryayi- 

 theinum equilaterale, M. australe, Cressa cretica of exotic origin ; 



* Quart. Journ. Geol. Soc, 1S70. 

 t Ifiland Life, 1880. 



