MOLLUSCA. PULMONIFERA. 255 



PULMONIFERA. 



TERRICOLA. 



Tentacula usually rounds and four in number. The eggs are 

 hatched on land. 



I. LiMACiDiE- Cloak and foot parallel, enclosing the viscera. 



a. Pulmonary cavity placed near the head, covered by a thick shield. 

 Arion 

 Limax. 

 aa. Pulmonary cavity near the tail, covered by a spiral open shell. 

 Testacella. 



II. CocHLEAD.4:. Clook and foot uot parallel ; the visceva Con- 

 tained in a spiral, dorsal protuberance, protected by 

 a shell. 



a. Foot with a lid for closing the mouth of the shell. 

 Cyclostoma. 

 Helecina. 

 aa. Foot destitute of a lid. 



b. Helicid^e. Last formed whorl larger than the penultimate 

 one. 

 c. Animal capable of retiring within the shell, the peristome of 

 which, with the exception of Achatina, becomes thick at 

 maturity. 

 d. Shell depressed or globose. 

 e. Peristome entire, raised on the pillar. 



Carocolla. 

 ee. Peristome inten'upted on the pillar. 

 Helix. 



dd. Shell turrited. 

 Bulimus. 

 Achatina. 

 cc. Animal incapable of withdrawing within the aperture of the 

 shell, the margin of which is thin. 

 Succinea. 

 Vitrina. 

 bb. PuPAD^. Last formed whorl nearly of the same size as the 

 penult one, or even less, giving the shell a subcylindrical 

 form. 



c. AVhorls dextral 

 Pupa. 

 Azeca. 

 Carychium. 

 ec. Whorls sinistral. 

 Balea. 

 Clausilia. 

 Vertigo. 



