TABLE OF GENERA. 285 



ACICULA. Shell subcylindrical, blunt, solid, brown ; mouth 

 ovate. p. 39. 



*** Shell smooth, half-ovate; mouth half-circular; inner lip 



transverse, acute. 

 NEBITINA. p. 43. 



c. Shell moderately thick ; edge of lips more or less thickened 



and reflexed. 

 * Mouth transverse. 



HELIX. Shell suborbicular or conical ; mouth lunate, or ovate 

 or circular. jr. 100. 



** Mouth oblong, longitudinal. 



BULIMUS. Shell oblong, striated ; mouth toothless. p. 145. 



ZUA. Shell oblong, polished ; mouth margined, toothless. 

 p. 154. 



AZECA. Shell oblong, polished; mouth margined, toothed. 

 p. 156. 



CARYCHIUM. Shell oblong, smooth, white ; mantle oblong, mar- 

 gined, sinuous. p. 190. 



CONOVULUS. Shell oblong, smooth ; mantle narrow ; pillar ob- 

 liquely plaited. p. 191. 



PUPA. Shell subcylindrical, striated, blunt ; mouth margined, 

 mostly toothed. p. 160. 



VERTIGO. Shell subcylindrical, striated, blunt ; mouth dex- 

 tral or sinistral, margined, mostly toothed. p. 167. 



BALEA. Shell turreted, striated ; apex acute ; mouth sinistral, 

 not plaited. p. 175. 



CLAUSILIA. Shell fusiform, striated ; apex acute ; mouth sinis- 

 tral, plaited. p. 177. 



E. Shell discoidal ; whorls revolving nearly on the same line. 



* Mouth lunate, sinistral, edge not continued- 

 PLANORBIS. Cavity simple. p. 230. 

 SEGMENTINA. Cavity crossed with transverse ridges. p. 245. 



** Mouth circular, dexfral, edge continued. 

 VALVATA. p. 34. 



