228 MOLLUSCA. 



culum) attached to the foot. The common Slugs 

 of our gardens and fields will illustrate the naked 

 (raster op ods ; while the Limpet, the Snail, the Peri- 

 winkle, the Whelk, and the Conch, will exemplify 

 those protected by a visible shell. 



The Class has been divided into eight or nine 

 Orders, distinguished chiefly by the form and' po- 

 sition of the lungs ; into these, however, we cannot 

 enter with minuteness, but must confine ourselves 

 to a brief notice of a few of the most remarkable 

 and interesting species. Of these we cannot select 

 a genus more universally known, at least in our 

 own climate, than that of 



Limax,* the Slug. 



It is distinguished by a lengthened body, covered 

 only in part by the mantle, which is confined to the 

 fore part of the back over the lungs; it contains 

 in general a small, flat, transparent oval shell, which 

 is found only on cutting open the mantle. The 

 lungs communicate with the air by an opening on 

 the right side of the mantle, which may be readily 

 seen in the living animal, expanding and closing. 

 The head is furnished with four tentacles, or fleshy 

 feelers, in which an exquisite sense of touch is 

 placed ; they can be withdrawn completely into the 

 body at will, or protruded by turning inside out, 

 as we pull off a stocking. The upper pair are the 

 longest, and terminate in little knobs, in each of 

 * Its ancient Latin name. 



