136 



four volutions, which are more swollen than those 

 of the P. impura, but not so much as those of the 

 P. similis, and the tip is more obtuse : aperture di- 

 lated and projecting forwards, without umbilicus. 

 The inhabitant is of a deep green colour, imparting a 

 blackish-green shade to the shell when filled with it. 



In ditches and canals. 



123. PALUDINA Stagnorum. Shell oblong, horn- 

 colour, rather acute, smooth, with five slightly 

 raised volutions : aperture oval, with a small um- 

 bilicus. 



Cyclostoma acutum. Drap. p. 40. t. I./. 23. 

 Helix stagnalis. Linn. Syst. p. 1248. 

 Helix Stagnorum. Gmel'in, p. 3653. 



Shell the eighth of an inch long, and a third part as 

 broad, pale greenish horn-colour, rather elongated 

 and taper, and ending rather acutely ; the primary 

 volution not proportionately larger than the rest : 

 aperture exactly oval, in nearly a straight line with 

 the spire, with a small perforation behind it. 



It appears to us that this is the hitherto obscure spe- 

 cies of Linne, who by an oversight had given to 

 two distinct species the name of Helix stagnalis. 



