SHELLS OF COMMON OCCURRENCE. 
BY WILLIAM WALLACE FYFE. 
Se 
Tue Limacide, or land-slugs, are represented con- 
chologically by the thin crustaceous shells found on 
dissection within their mantles, being, as every- 
body familiarly knows, outwardly destitute of shell. 
This shield is protective of the cavity employed in 
respiration. Figs. 1, 2,3, and 4 represent four of 
these shields, extracted from the milky, yellow, 
tree, and spotted slugs respectively (Limaz agrestis, 
L. flavus, L. arborum, L. cinereus). 
These creatures, as every lover of a garden too 
well knows, are powerful vegetable feeders, making 
their appearance in damp weather in multitudes 
hke an Egyptian plague. Their destructive voracity 
enables them to secrete an exuberance of white 
milky mucilage from their bodies, to discharge this 
copiously when irritated, and to mark their devour- 
ing tracks in their slime. Like linseed and other 
