TABLE OF GENERA. 285 



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

 ovate. — p. 39. 



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



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. — p. 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. 



Baxea. 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, dextral, edge continued. 

 Valvata. — p. 34. 



