131 



Shell nearly a quarter of an inch long and as much 

 broad, globular, thin, light horn-colour, very finely 

 striate longitudinally, and marked with some ob- 

 scure circular lines : spire of four volutions, tumid 

 and deeply defined, and having much the appear- 

 ance of a Trochus, with a deep central umbilicus 

 beneath : operculum dull greyish white, penetrating 

 the mouth. 



In canals and ponds, but not common. 



115. Valvata Spirorhis. Shell slightly concave 

 above, and umbilicate beneath. 



Valvata Spirorbis. Drap. p. 41. t. 1./. 32, QQ, 



■ Brard,p. 187. t. 6.f. 15, 16. 



Helix cristata. Mont. p. 46. rign. \.f. 7, 8. 

 Turbo cristatus. Turton, Diet. p. 227. 



Shell about the tenth of an inch in diameter, pale 

 horn-colour, striate transversely, with three volu- 

 tions ; the upper surface a little sunk : the under 

 side umbilicate, so as to expose the interior volu- 

 tions. 



In ditches and canals, on aquatic plants. 



