50 LAND AND FRESH-WATER MOLLUSKS. 
The colour of LZ. Sowerbii is yellowish, speckled 
with brown; head and horns black ; shield as if 
minutely warted with a furrow near its margin. 
Shell oval, thickened, two or three lines long, 
and one and a half to two broad. 
Fig. 13.—Limux Sowerbii. 
The keeled slug, when at its greatest exten- 
sion, is about three inches in length; its graceful 
and lanceolate figure, neat yellowish-brown hue, 
and the amber-coloured keel, make it really not 
such a disagreeable object for a slug. The 
hinder portion of the body is much compressed ; 
the shield measures three-quarters of an inch. 
When touched, it withdraws the head under the 
mantle, and contracts to about an inch anda 
half in length, as in fig. 13. In drought they 
exhibit greater contractedness, and the smaller 
specimens when covered with particles of soil 
and dust, resemble so many pellets of mould. 
The keel is folded into transverse wrinkles on 
the contraction of the animal. The dental for- 
mula is #22, 
