48 



and fleshy to the feel. The true slugs are not pos- 

 sessed of a shell, yet they have a calcareous shield, or 

 the rudiments of a shell, which is buried in the mantle 

 of the animal; this mantle covers the anterior part of 

 the slug, being that portion situated at the back of the 

 head, and is a means of protecting the breathing cavity. 



The slugs have all four retractile horns or tentacles, 

 having in the upper ones a pair of eyes. A great exu- 

 berance of mucilaginous matter is secreted from their 

 bodies. 



The slugs live upon vegetebles, yet, when hard- 

 pressed for food, will devour dead earth-worms. 



This particular branch of the British mollusca are, 

 to all outward appearance, devoid of shells, yet, when 

 the animals are dissected, a thin crustaceous shield is 

 found deposited in the mantle of the slug. 



Arion. 



The shell is undeveloped, being an oblong mass of a 

 granular calcareous, or horny substance, which is hid 

 in the mantle of the animal. 



The Arion tribe is provided with four horns, having 

 eyes placed on the upper pair. 



Arion Empiricouum (The Common Arion.) Firussac. 



This Arion varies considerably in its colour, being 

 sometimes black, at others nearly while, yellow, and 

 reddish brown. It is frequently brilliant and shining, 

 and may be said to be a handsome species. The 

 variety in colour does not appear to be occasioned 

 either by the locality or the food eaten by this species, 

 for these many varieties occur wherever Arion empiri- 

 corum is found. 



It ranges, in its length, from 3 to 5 inches. The 

 boms are all' of an exceedingly dark blue colour, the 



