1.26 Clici'pman: Palaeozoic Genus Hercynella. 



Uercynella, but of the molluscs and brachiopods occurring in the- 

 Victorian Yeringian, seems, therefore, entirely due to the fact that 

 tlie waters were frequently rendered turbid by the periodic dis- 

 charge of terrigenous material by rivers, and possibly also by coast 

 erosion, a condition which acts severely on lime-secreting organisms, 

 a fact that can be proved by examining the shore-faunas of land- 

 locked and mud-swept bays. at the present time. 

 The conclusions drawn from the above data are : — 



1. — That the Hercynellas of the Victorian Yeringian were of 



marine habits, as proved by the associated fauna. 

 2. — That the sediments of locality B 23, in which Hercynella 

 occurs, were laid down under fairly deep-water marine 

 conditions, but the areas of sedimentation may have 

 been periodically subjected to invasions of mud brought 

 down by rivers. 

 3. — That the lime-secreting fauna of the Yeringian mud- 

 stones tends to prove, by the thin shells, that the terri- 

 genous element in the Yeringian sea was so marked as 

 to considerably lower the amount of carbonate of lime: 

 available to those organisms. 



