34 Our British Snails 



behind. The shell is distinctly formed in all but 

 Arion, in which.it is absent or represented by a 

 few granules. Arion has no dorsal keel. Amalia 

 has one all down the back. In Limax and Agrio- 

 limax it is confined to the caudal part. Other 

 differences are only discovered b}^ dissection. 



One may also here note that to preserve slugs 

 is difficult, and the best plan is to have a coloured 

 drawing made of them when extended. Other- 

 wise they may be drowned in cold water, cleaned 

 of slime with a soft brush, and then preserved 

 in glass tubes with diluted formalin or alcohol. 

 Or, after drowning, they may be skinned and the 

 skins dried on a card and varnished. Note also 

 that most slugs have many variations in colour 

 and markings. 



Testacella haliotidea. — This genus of slugs forms 

 a link between the naked slugs with rudimentary 

 shells within, and the snails which live within 

 their shells. The name Testacella, or little 

 shell, was given by Cuvier in 1800, because this 

 slug has a small shell at the end of the tail. Halio- 

 tidea means having a shell in the form of the 

 marine shell Haliotis, the meaning of which again 

 is the ear-shaped seashell, often called " Venus' 

 Ear." It is subterranean in habit, and lives on 

 worms. It should be looked for on the surface 

 on damp nights, or is found when digging. Its 

 length is 3 inches at most. Pale yellow in colour. 

 See the illustration on page 35. 



