318 PROCEEDINGS OF SECTION D. 



Amarantacese, Verbenacefe, which are more largely represented in 

 this region than in the rest of Australia, whilst the Order 

 Myoporineje, which is essentially Australian, has its head-quarters 

 within this region, Of negative characters, perhaps the most 

 striking is the absence of Epacrids, one extra-limital species, 

 however, just reaches the outskirts of the region. 



As to genera the following are either peculiar or attain their 

 greatest development in the Region. 



I. — Those of Endemic origin. 



Stenopetalum, Geococcus (monotypic), Menkea, Hannafordia, 

 Diplopeltis, Macregoria (monotyjnc), Ptilotus, Dysphania, Didy- 

 manthus (monotypic), Babbagia, Gunnia, Templetonia, Ptychosema 

 Ctianthus, Fetalostylis ( monotypic J, Swainsonia, iSti/lobamim, Galo- 

 tis, Pterigei'on, Erodiopliyllum (monotypic), Dimorphocoma (mono- 

 typic), Catosperma, Notoneritim (monotypic), Dicrastyles, New- 

 castlia, Gnephosis, Cephallpterum. (monotyjnc), Chthonocephalus, 

 Millotia, 31yoporum, Ertmophila, NeuracUne, Astrebla. 



II. — Those of Exotic origin. 



Sida, Abutilon, Tribuhis, Abriplex, Bassia, Kochia, Crotalaria, 

 Cassia, Helipterum, Eragrostis, Triodia. 



Whatever value we may assign to the Eremian Flora in respect 

 of its exoteric relations, there cannot be a doubt that it occupies 

 an excessively dry region which is an impassable barrier to the 

 interchange of Autochthonian and Euronotian types. The 

 nature of the barrier which isolates the Autochthonian Region 

 has hitherto been overlooked. The only way of migration 

 between two extreme regions may possibly have been by the 

 former extension of the southern coast line, during Post-Miocene 

 times, indications of which are afforded by the truncation of 

 the Old Tertiary beds of the Great Australian Biglit, which 

 present a perpendicular front to the sea, varying from two 

 hundred and hfty to one hundred and tifty feet elevation, for a 

 length of three hundred miles, i.e., from the Head of the Bight 

 to Point Calver. i his suggestion that the Autochthonian Region 

 may have extended southward and westward of its present limits, 

 seems to be demanded by cei'tain analogies which Kangaroo 

 Island and Port Lincoln present with it.* 



Has this climatic barrier always existed during the epoch of the 

 existing floras or their immediate ancestors ? The answer is, no ; 

 though a barrier of some sort has intervened fromi Pre-Cretaceous 

 times till an absolutely recent period. 



Firstly. — Marine Cretaceous beds are wirlely disti'ibuted in 

 Central Australia, they occupy a very large portion of the eastern 

 section of the Eremian Region, probably underlie the Desert 



*Thoug-h the dejjth of water about the Great Australian Bight is generally twenty 

 fathoms at from one to two miles off shore, and thirty fathoms at five or six miles, yet 

 Yatala Reef thirty-ei^rht miles seaward from Fowler Hay, affords soundings at ten fathoms ; 

 other reefs and islets occur to the south-east of this place which may be regarded as 

 remnants of an old coast line. 



