SECTION III. 



THE CLASS OF GASTEROPODA OR GASTEROPODS. 



THE Gasteropoda are mollusks whose ventral side serves 

 them as a sort of foot, by means of which they creep along. 

 The name is from the Greek gaster, stomach, and pous, a 

 foot. This Class comprises about three-fourths of all the 

 Mollusca. 



FIG. 542. 



Internal structure of a Gasteropod Snail. 



a, mouth; &,&, the foot; c, vent; d,d. lung; e, stomach covered by the salivary 

 glands; /./; intestine; g, liver; h, heart; i. aorta; j, gastric artery; I, hepatic artery; 

 jfc, artery of the foot; m,m,m, abdominal cavity supplying the place of a venous sinus; 

 n,n, irregular canal connecting the abdominal cavity and the lung; 0,0, vessel carry- 

 ing the blood from the lung to the heart. 



Most of the Gasteropods have a shell ; and as this is 

 made of only one piece or valve, they are often called 



