PULMONATA, O 



b. Front of body, head and tentacles distinct from and retractile 



into the mantle. 



* Young with an operculum, at length deciduous, and protected 

 by an external shell which afterwards becomes hidden in 

 the shield-like mantle of the adult. 



2. Cryptellad^. 



** 



Young and adult without any operculum. 



3. Testacellid^e. Foot without any subcaudal gland. Teeth 

 numerous, slender, conical, distant (fig. 1). Jaws none. 

 Body and shell spiral, subcaudal. 



Fig. 1. — Teeth of Testacellus. 



4. Arionid^. Foot with a distinct gland rather above the tip. 

 Teeth numerous, four-sided, close together on the lingual 

 membrane. Jaw homy, distinct. 



3. HeliciDj^s. Foot tapering behind, without any subcaudal 

 gland. Teeth numerous, four-sided, close together on the 

 lingual band (fig. 2). Jaw homy, distinct. Body and shell 

 subcentral, dorsal. 



Fig. 2. — Teeth of Achatina fulica. 







7"^ - - - I e I 



In these figures, c represents the central, I the lateral, and u the 

 exterior lateral teeth. 



b2 



