Plate III. 



Vol. IV. 



14 



16 



17 



Zonites mtidus Miill. — i, Dart-sac and adjacent parts, x 7. 2, Dart, x 10; 

 3, Side view of same showing the twist. 4, Dart in its sac. 



Zonites excavatics Bean. — 5, Dart-sac, x 7. 6, Dart, x 10. 7, Side view of 

 same. 8. Head more enlarged. 9, Dart in its sac. 10, A deformed dart-sac. 



Helix virgata Da Costa. — 11, Dart-sac, x 3. 12, Another with indented 

 end. 13, Dart, X 7. 14, Section of head. 15, Head more enlarged. 16, 

 Immature dart. 17, Base of dart. 



