SLUGS. 69 
and the internal shell claw-shaped. In Testacella 
we have a near approach to the snails, and | 
through Vitrina is connected with them; the 
shell is small, ear-shaped, placed externally at 
the hinder extremity of the body, and covers the 
mantle, beneath which, on the right side, is the 
respiratory orifice. 
Genus ARION. 
Arion was a horse remarkable for its speed, 
but our Arion is remarkably slow. 
Arion ATER—(the Black Slug) (P1.V., fig. 31)— 
is familiar to all as a common object of our gar- 
dens and waysides, and is also too well known to 
the gardener, as being more or less injurious to 
the early cabbages and other garden produce; 
and in the autumn as one among other mollusks 
_ that mutilate and render repulsive the fruits of 
that season. Dead animal matter—even that 
of their own species—does not come amiss to 
them; they also feed on the common earth- 
worm. 
- The adult animal is usually brownish or 
ereyish-black; at other times brown or red- 
dish; the young individuals are grey, whitish, 
bluish-white, or yellow-coloured. It attains a 
leneth of from three to five inches. The shell 
is composed of loosely aggregated calcareous 
particles, 
