128 



111. PHYSA alba. Shell quite white, oval, inflated, 

 with the volutions tumid and exserted : aperture 

 roundish-oval. 



Physa alba. ZooL Journ. i. p. 363. t. 13. f. 3. 



Shell about the size of the last, but is quite white, 

 with the volutions more tumid and oblique, and 

 deeply defined by the suture : pillar spread, with- 

 out flexure in the middle, but forming a longitu- 

 dinal hollow behind it. 



Found in the river Towyn in North Wales. 



"j~ 112. PHYSA rivalis. Shell oval, horn-colour, with 

 a rather prominent acute spire: aperture oval- 

 oblong. 



Bulla rivalis. Linn. Trans, viii. p. 126. t. 4./. 2. 



Shell larger than the Physa foul'mal'is, and differs in 

 being exactly oval, with the spire prominent and 

 acute. 



Said to have been found in Hampshire by Mr. James 

 Hay, but is a very doubtful shell. 



113. PHYSA Hypnorum. Shell horn-colour, oblong, 



