Gastropoda. 137 



CHARACTERISTICS OF THE GASTROPODA. 



1. The gastropods have a foot which is developed as a 

 broad, flat, creeping disk. 



2. There is usually a well-developed head, with eyes and 

 tentacles. 



3. The majority have a univalve shell, but this is some- 

 times lacking. 



4. Body often unsymmetrical. 



5. There is a lingual ribbon. 



