PNEUMOBRANCHIATA. 



FAMILY I. 



LIMACID^. 



THE SLUGS. 



Characters. Body elongated, sub-cjlindrical, upper 

 surface convex, lower surface flat, and consisting through- 

 out its whole length of a muscular disk or plane, bj the 

 action of which the animal crawls. Back wholly or par- 

 tially covered with a fleshy mantle or cuirass, oval in shape 

 and differing in size and position in the difierent genera, but 

 in all of them protecting the respiratory and circulatory 

 organs. Integuments transparent, and without much 

 consistence, containing numerous glands with intervening 

 furrows ; the glands secrete a copious watery mucus, and 

 the furrows, anastomosing with each other, form a some- 

 what symmetrical network of channels, which convey the 

 mucus to every part, and constantly lubricate the whole 

 surface. Mouth anterior, the head provided with four 



VOL. II. 1 



