138 INTRODUCTION TO ZOOLOGY CHAP, x 



Family ]. Helicidae (Garden Snails and the Black Slug). 

 Land forms, with shell usually present, 

 though represented only by calcareous grains 

 in the slug ; radula with a central tri-cuspid 

 tooth. 



Helix, the Garden Snails. 

 Arion, the Black Slugs. 

 Bulimus, the " Greedy " Snails. 



Family 2. Pupidae. Forms in which all the whorls of 

 the shell are of about equal breadth ; the 

 aperture of the shell usually has one or more 

 teeth at its margin. 



Pupa, the " Puppet Snails " or Chrysalis Snails. 

 Vertigo. 



Family 3. Testacellidae. Slugs in which the shell is 

 usually present, though small, and is placed at 

 the end of the long body. 

 Testacella, the Carnivorous Slugs. 

 Family 4. Limacidae. Forms in which a rudimentary 



shell is present, but covered by the mantle. 

 Limax, the Grey Slugs. 



Older II. PROSOBRANCHIATA. Water snails breathing by means of 

 a single gill. They have one pair of tentacles, and the sexes 

 are distinct. 



Littorina, Periwinkles. 



Paludina, Fresh-water Winkles. 



Bithynia. 



Buccinum, Whelks. 



Cypraea, Cowries. 



Murex. 



Patella, Limpets. 



PRACTICAL NOTES ON LAND SNAILS AND SLUGS 



These may be quite satisfactorily kept in a box of damp earth, 

 partly covered by a piece of turf. Over the open box should be 

 placed a sheet of glass. Some cabbage or lettuce leaves should be 

 put in for food, but these must be renewed every day. 



After a time eggs may be looked for just below the surface 

 of the earth. If possible, their development should be followed ; 

 care must be taken that they do not dry. Testacella, the Car- 

 nivorous Slug, will feed on the earthworms in the soil ; its eggs 

 are large and oval, and are laid singly. The behaviour of both 

 snails and slugs at the approach of winter should be noted. 



