568 president's address. 



of Tasmania for over fifty miles in a direction N. 7° W* The 

 axes of the Lower Silurian in the north-west of Tasmania conform 

 with those of the Archaean Group, which strike, as already stated, 

 N. 25° W. 



In Victoria the Lower Silurian sediments have been very 

 strongly folded, their strike varying from N, to N.W., the preva- 

 lent direction being N.N.W., and their dip being from 60° to 

 vertical. This folding took place partly before the deposition of 

 the Upper Silurian strata,! though no marked nnconformability 

 is visible between the two series. It is noteworthy that the trend 

 of these folds is nearly at right angles to the trend of the Main 

 Divide. 



In the Mount Macdonnell Ranges the axes of folding strike 

 persistently E. and W., but no evidence has as yet been obtained 

 to show exactly when this folding took place. The absence, as far 

 as is known, of Lower Silurian strata from New South Wales is 

 probably due to the fact that its Main Dividing Range lies to the 

 east of the general strike of the Lower Silurian strata of Victoria, 

 which trend towards the flat country between Wagga and Hay, 

 which is largely covered by Tertiary and Post-T"ertiary deposits, 

 which would conceal from view the underlying rocks, possibly of 

 Lower Silurian Age. 



In New Zealand the Aorere Series was certainly folded and 

 denuded before the deposition of the Maitai rocks, approximately 

 along axes parallel to the principal axis of the South Island. 



Summary of Loiver Silurian Epoch. — The sediments of this 

 portion of the Silurian period show that in New Zealand and 

 Victoria there were seas of some depth, on the floors of which at 

 some distance from land the skeletons of graptolites accumulated 

 in such numbers as to blacken the marine muds. The earliest 

 Australasian Phyllopods are represented by the Victorian forms 

 Ilymenocaris and Lingulocaris. 



* Loc, cit. p. 64. 

 t f. Murray, loc. cit. p. 43. 



