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, 
N'eeitina. 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 oblongs 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., dextral., edge continued. 
Valvata. — p. 34. 
