90 HELICIM:. 



Helix ; for while their edge teeth show no appear- 

 ance of bifurcation, the heel to the apex may pos- 

 sibly be looked upon as an approach toward it. 

 Their sagittate central tooth corresponds with that of 

 Vitrina ; and a similarly shaped central tubercle in 

 Helix fulva connects them with the true Helices, 

 which have a simple aculeate tubercle. 



The jaw is like those of Limax and Vitrina, broad, 

 smooth, with a central rostrum. 



The animal can entirely withdraw itself into the 

 shell ; and this genus is at once known from the 

 Helix by the thinness and generally polished state 

 of the shell, and also by its being depressed and 

 destitute of any internal rib round the edge of the 

 mouth. 



It is intermediate between the Helices and the 

 foreign genera Stenopus and Nanina of the family 

 ArionidcB. The animal also resembles the latter in 

 some respects, but wants the* gland on the end of the 

 foot. According to M. Moquin Tandon, there is a 

 small longitudinal slit at the end of the tail of 

 Zonites nitidus. It is very probable that other 

 peculiar characters will be found when the animals 

 of the different species of Helicida have been de- 

 scribed and compared together, as Mr. Nunneley has 

 so excellently well done with the species of slugs. 



a. Shell depressed, yellowish; whorls moderately en- 

 larging ; umbilicus large. ( Aplostoma.) 



25. 1. ZONITES alliarius. Garlic Snail. Shell nearly 

 flat, slightly globular, thin, transparent, horn- 

 coloured, very shining, nearly smooth ; whorls 



