120 
Clarke. — Xatunil Regions in ll'estcrn Australia. 
III. Description of the Natural Regions. 
1. Xullarhnr. Cloolog-ic-allv, this region is very simple aiio 
uniform, ])eing composed of Tertiary limestones underlain by sandv 
rocks {Maitland, 1919, a., ]>. 48), from -which in places is obtainec 
sub-artesian water of poor (piality. Equally simple is the topograplr 
of the great treeless plain traversed by the Trans-Australian rail! 
wav. The vegetation, at least from the general observer's point O; 
view, is sparse and uniform. The rainfall is less than 10 inches- 
except along a narrow coastal strip which is neither large enough no 
sufficiently distinct in its possibilities to be separated regionall. 
from the limestone country farther inland. The Xullarbor Region 
se.ins unlikely ever to su]>port more than a very sparse pastorn 
community. 
2. TJtc U’Jirat Belt. This region includes the Yilgarn Goldhek' 
with the mining centres of Spoilt hern Cross, Bullfinch and "Westonir 
of which comi»lete geological surveys are available (Blatchford an 
Honman. 1917, and literature there cited), but most of the rc 
luainder, except the gold-cop}ier centre Ravensthorpe. has still t 
he ]u-os])ected and geologically surveyed. Bo far as known, thi' 
area is conqtosed of crystalline rocks, chiefly acid, but with mine 
<1 velopments of dark coloured basic rocks in Avhich most of tlir 
mineral wealth occurs. These rocks are supposed to be Pro. 
Chnnbrian, although there is no clear proof of their age (Clarke, 192- 
p. lo). Along the southeui coast are patches of Tertiary or sti 
later rocks covering areas too small to be separated in this dhi- 
cussion. Topographically this region is the southern part of tli)'' 
Bieat Plateau of Western Australia (Jutson, 1914, p. 19), and pivli 
.-•eiits the usual characteristics of that upraised peneplain, ineludini:i 
the oft-described salt ‘‘lakes. '' Near the coast the topography bo- 
comes more varied, with several inlets indicating recent depressioi), 
and with cons])icuous east-and-west trending ranges (the Barrens . 
In this southern ]uirt of the region Mallee thickets (Gardner, 192;- 
2"). Vol. VII, ]L 48) are perhaps more abundant than elsewhere i> 
the State. The soil is more fertile than that of the Xullarbor regiru 
— as follows from the nature of its constituent rocks. The average 
annual rainfall ranges from 10 to 20 inches, and most of it fal ^ 
in the winter. The ])redominant vegetation of this region is tl ' 
Salmon Gum-Morrel association to the east, passing into the Wandf )i 
on the west, which in turn grades into the Jan-ah forest of tT?i 
‘‘South-West'' outside the limits of the region (Gardner, Vol. VP.' 
p. 40). The eastern portion of the wheat belt is, despite a slights 
smaller rainfall, more easily settled than the Wandoo section, whu M 
suffers from the disability of being the chief ‘‘poison country’^ 
the State. ‘‘X’early all the known junson plants belonging 
Gastrnlohium and O.riilohium are characteristic of Wandoo unde- 
