absent from the section 

 on Yorke Peninsula. 

 This remarkable hiatus 

 in the geological sequence 

 must be accounted for in 

 some way. 



The following sketch 

 (fig. 4) represents the 

 occurrences and relative 

 thicknesses of the beds 

 in the neighbourhood of 

 Ardrossan, Maitland, and 

 Port Victoria: — ■ 



In this table of 

 strata the entire Cam- 

 brian System is repre- 

 sented by about 300 

 feet in this locality, as 

 against, probably, 15,000 

 feet on the eastern side 

 of Gulf St. Vincent. The 

 Archaeocyathinae beds 

 represent a late stage in 

 the Cambrian terraine, 

 and they form a geologi- 

 cal horizon which in other 

 localities is both under- 

 lain and overlain by con- 

 formable sediments of 

 Upper Cambrian Age. 

 The missing upper mem- 

 bers can be easily 

 accounted for by de- 

 nudation, but how can 

 the absence of the under- 

 lying beds be explained ? 



The most nlausible 

 explanation that occurs 

 to the author is that 

 during the long Cam- 

 brian Period deposition 

 was accompanied in South 

 Australia by a geosyn- 

 clinal downfold that 

 formed an extensive 

 trough in a north 

 and south direction, 



