xvi 



CONTENTS. 





Page 



Order III. — Trachelipoda 



- 163 



DlVTSTON T pHVTftPH AfA 





Family I. — Colimacidce 



- 164 



38. Helix 



- 165 



39. Carocolla - 



- 170 



40. Anastoma - 



- 171 



41. Helicina 



- 172 



42. Pupa 



- 172 



43. Clausilia 



- 173 



44. Bulimus 



- 174 



45. Achatina 



1 7ft 

 - ± i O 



46. Succinea - 



1 TO 



47. Auricula 



l on 

 LOU 



48. Cyclostoma - 



1ft 1 



lOl 



Family II. — LymnceidcB 



- 181 



49. Planorbis 



182 



50. Physa 



- 183 



51. Lymnea 



- 183 



52. Ancylus 



- 185 



Family III. — Melanidce 



186 



53. Melania 



- 186 



54. Melanopsis 



- 187 



Family IV. — PeristomidcB 



- 187 



55. Valvata 



- 188 



56. Paludina 



- 188 



57. Ampullaria 



- 189 



58. Ampullacera 



- 191 



Family V. — Neritidce 



- 192 



59. Navicella 



- 192 



