113 



Shell an inch in diameter, thick, usually of a rusty- 

 brown colour above and whitish underneath, ob- 

 liquely striate : volutions five, the outer one round- 

 ed, with a deep umbilicus on the upper side ex- 

 posing three of the volutions ; under surface a 

 little concave and whitish : aperture rather oblique, 

 rounded, as high as broad. 



In muddy streams and ditches. 



96. PLANORBIS contortus. Shell nearly flat above, 

 deeply umbilicate beneath : aperture very narrow 

 crescent-shaped. 



Planorbis contortus. Drap. p. 42. t. I./. 39 41. 



. Brard, p. 157. t. 6./. 1214. 



Helix contorta. Mont. p. 457. t. 25. /. 6. 



Shell about two tenths of an inch in diameter, and 

 one tenth in thickness, brown horn-colour, and 

 when free from accidental incrustations exhibiting 

 in water a bronzed or gilt lustre : volutions five, 

 remarkably compact and equal in size ; the under 

 surface with a large and deep umbilicus : aperture 

 very narrow crescent-shaped, wider than high, not 

 produced on either side. 



