Ill 



/ 



bilicate beneath ; the outer volution subcarinated 

 near the middle. 



Planorbis complanatus. Drap.p. 47. t. 2./. 20 22. 



Brard,p. 161. t. 6./. 4. 



Helix fontana. Montagu, p. 462. t. 6./. 6. 



Shell not a quarter of an inch in diameter, of a dark 

 or whitish horn-colour, very convex above with 

 the centre flattened, flat beneath with a central 

 umbilicus ; the outer volution slightly but rather 

 sharply carinate near the middle. 



In clear stagnant waters. 



94. PLANORBIS imbricatus. Shell flat above, um- 

 bilicate beneath, with a spinous ridge round the 

 outer volution : aperture oval, united all round. 



Planorbis imbricatus. Drap. p. 44. t. l.f. 49 51. 

 Brard,p. 163. t. 6./. 10, 11. 

 Helix nautileus. Mont. p. 464. t. 25. f. 5. 

 Turbo nautileus. Linn. Turt. Diet. p. 227. 



b. with the transverse laminae remote, and the 

 shell smaller. 



Planorbis cristatus. Drap.p. 44. t. 2. /.I 3. 



c. with the transverse laminae obliterated. 



