96 PROCEEDINGS OF THE MALACOLOGICAL SOClETy. 



down than Bermondsey, whilst, in the Lea Valley, Canning Town is 

 its limit. 



Practically all the shells show only too plainly the corrosive action 

 of the decaying vegetable remains in which they were buried This 

 is particularly noticeable in Unio tumidus and Neritina fluviatilis. 

 The examples of the former were so decayed that it was impossible 

 to preserve them, although the species could be easily determined, 

 whilst the two specimens of the latter are nearly destroyed, only the 

 thicker part of the shell remaining. 



The deposit is without doubt a shallow-water one out of the main 

 current, and the presence of silt demonstrates that running-water did 

 occasionally reach the spot. There is a total absence of all brackish- 

 water forms, and this, in conjunction with the depth, clearly shows 

 that the deposit was laid down in early Holocene times, when England 

 stretched far out into what is now the North Sea, and the tidal waters 

 were probably miles away. 



