SLUGS. Pigs 
brought near them they shrink back, but for a 
moment, and leisurely pursue their way; by the 
aid of this light they are pretty objects in their 
almost transparent flesh variegated with mark- 
ings. It also occurs in damp places, beneath 
stones, and among plants in woods. 
I. flavus is one of the few European Pulmo- 
nifera introduced to America; it occurs rarely in 
Portland, Maine. 
Limax acrustis—(the Field Slug) (PI. V., fig. 
30).—The form is oblong, very convex above, the 
shield large, broader behind, marked with concen- 
tric lines ; the body on the upper side of a yellow- 
ish-grey or pale brownish-yellow, often mottled 
with dusky and whitish, with numerous longitu- 
dinal interrupted ridges ; it varies considerably 
in colour, being sometimes whitish or cream- 
coloured, or grey or dusky; back with a short 
keel, bent obliquely towards the end; the under 
side pale grey, margined with yellow. Length 
about an inch and a half; shell one line and a half 
long and one broad, concave above, concen- 
trically wrinkled, with a membranaceous margin. 
The horny jaw is crescent-shaped, with blunt 
ends; the exterior surface is marked with nume- 
rous slight longitudinal ribs, which project over 
_ the cutting edge; the dental formula is 22-22, 
the central plate is longer than wide, carrying 
a tooth as long as itself, shouldered at the base ; 
