600 president's address. 



square miies, about -^~ of the whole area of Australia and 

 Tasmania. 



Lower Silurian rocks have been iclentilied in Victoria, Tas- 

 mania, Central South Australia, and New Zealand. They are 

 characterised by abundant graptolites, and trilobites, with the 

 addition, in Tasmania, of corals and cephalopods. Ripple-marked 

 sandstones and conglomerate beds indicate shallow water condi- 

 tions for their accumulation in Tasmania, and at the Mount 

 Macdonnell ranges conglomerates indicate similar conditions, 

 temporary cessation of sedimentation on deepening of the ocean 

 being marked by beds of limestone. In New Zealand, on the 

 other hand, the Lower Silurian sediments may have accumulated 

 in seas of some depth. 



The amygdaloids of Wooltana and the Mt. Arrovvsmith Ranges 

 in South Australia may represent contemporaneous volcanic 

 outbursts. The folding in Tasmania was on axes N. by W. and 

 N.N.W., in Western Victoria on N.N.W. axes, and in the Mac- 

 donnell Ranges on E. and W. axes. 



It was perhaps daring this epoch that a third axis commenced 

 to develop which may be termed the Kosciusko Axis havirig 

 approximately a meridional trend. There was probably land at 

 this time in the Southern portion of the Cordillera region of New 

 South Wales, and in Victoria, Tasmania, and South and West 

 Australia. In New Zealand the Lower Silurian were folded on 

 the same axes as the Pre-Silurian following for the most part the 

 trend of the Southern Island, but the date of the folding in New 

 Zealand cannot be determined further than that it took place 

 before the Carboniferous or Permo-Carboniferous Period. 



Rocks of Upper Silurian age are known to exist in Tasmania, 

 Victoria, New South Wales, and possibly in New Zealand. In Vic- 

 toria their thickness added to that of the Lower Silurian has been 

 estimated by Mr. Selwyn as 35,000ft. The sun- cracked flaggy 

 sandstones in the Yass district of Upper Silurian Age prove con- 

 clusively that there was some land in the southern portion of New 

 South Wales during that epoch. The missing sub-kingdoms of 

 the animal kingdom, the Echinodermata and the Vertebrata, are 



