GOG AUSTEALIAX SPECIES OF PHOEOXIS, 



and fringed with level plains, and these are again covered with 

 vegetation. 



This though composed of the same or similar genera as that of 

 the preceding periods is far more luxuriant. Dark humus 

 accumulates during long periods of undisturbed growth, until a 

 river flood, or another rise of the lake covers it with mud. This 

 being again exposed, the process is repeated, until by slow degrees? 

 and after many oscillations of rise and fall, many successive Coal 

 seams one above the other, each wdth its foot- clay, and roof of 

 shale or sandstone, are buried beneath the waters, and the pro- 

 duction of coal in these regions is ended. 



For once more, and for the last time, the lake has encroached 

 greatly and rapidly upon the shore, and its waves once again beat 

 directly upon the sloping bases of the hills. 



The same vegetation still clothes the land, but there are no 

 levels in which its debris can accumulate, and what woody matter 

 is washed down into the water is soon comminuted by the con- 

 stant shock of the shore waves. The never ceasing erosion of the 

 land, continued centuries after centuries, perseveres in' lowering 

 the mountains into an undulating land, with its eastern and 

 northern slopes dipping below the sandy shores of the lakes. 

 For vast beds of sand formed from the waste of the continent, 

 swept down into the lake by rivers, and transported by the shore 

 wash to right and left of their mouths, have now silted up with 

 a final deposit, (the coping stone as it were of the whole building), 

 all the series of rocks w^hose formation we have been witnessing 

 in imagination. 



This is the commencement of the Hawkesbury Period. 



Peeliminaey :n'ote on ax ArsTEALiAi^' SPECIES OF Plioronis 



{Ge])liyrea ^ Tuhicola.'') 

 By William A. Haswell, M.A., B.Sc. 

 The aberrant genus JPJioronis, whose remarkable relations to 

 the Gepltyrea on the one hand, and lo the Entop-oct Brijozoa on 



