MOLLUSKS. 329 
of these animals, I will give you the anatomy of one of 
them in Fig. 261. One of the valves is removed. You 
Anterior 
Muscles 
Mantle. 
Tentacula. 
Mouth. 
Nerves 
= 
a 
7) 
¢ 
Bey 
Anterior 
Foot. Ganglia. 
Intestine. = =o eS : i), i oer oe ais | Stomach. 
/-- Shell. 
Stomach, 
Posterior 
Ganglion. 
Gills. 
Posterior 
Muscle, 
Mantle. 
Respiratory Tubes. 
Fig. 261.—Anatomy of an Acephalous Mollusk. 
see the mantle, fringed all around its edge. This lines 
the whole shell, and covers the animal. It is its skin. 
You see the two muscles that, by their contraction, bring 
the valves together, and the fleshy foot, which can be 
made to protrude when the valves are left to go apart by 
the action of the elastic hgament. This foot, which is 
