262 



MOLLUSC A. 



CHAPTER XVllI. 

 MOLLUSC A, 



I. 



ANODON. 



-HELIX. 



Phylum .... Mollusca (p. 282). 

 Class Gastropoda (p. 283). 



Fig. 184.— Lateral View of the Roman Snail {Helix popiatia). 

 Natural size. 



Ocul" 

 Tenta( 



Note the creepingToot, spiral shell and head with tentacles. 



• Helix pomatia (the' edible or Roman snail) is slightly 



larger than ILelix aspersa (the garden snail) and more con- 



g . venient for dissection. It does not differ in ; 



essential features. The body is of a dark 



greenish- slate'^colour, and the shell of a uniform pale drab. 



The snail is a vegetable- eater and mostly nocturnal in its 



habits. It hibernates in the winter, when it closes up the 



Habits aperture of the shell by an epiphragm of chalky 



matter and hardened mucus. It is in most 



features a piano- symmetric animal but its symmetry is in 



