THE ALIMENTARY CANAL. 81 



Fig. 45 — Anatomy of a Gasteropod (Snail) : a, mouth ; &, foot ; c, anus ; d, lung ; 

 e, stomach, covered above by the salivary glands ; /, intestine ; g, liver; 7t, heart ; 

 i, aorta; j, gastric artery; Z, hepatic artery; k, artery of the foot; m, abdominal 

 cavity, supplying the place of a venous sinus ; n, irregular canal communicating 

 with the abdominal cavity, and carrying the blood to the lung ; o, vessel carry- 

 ing blood from the lung to the heart. 



valve, but is not so clearly distinguished from the gullet, 

 so that regurgitation is easy. 42 Indeed, it is common for 



ghikealmn / o 



Fig. 46 Anatomy of a Lamellibranch (Mactra) : a, shell ; ft, mantle ; c, tentacles, or 



lips ; c?, mouth ; c, nerves ; /, muscles ; g, anterior, and n, posterior ganglion ; h, 

 liver; i, heart: k, stomach; Z, intestine passing through the heart; w, kidney; o, 

 anal end of the intestine ; p, exhalent, and g, inhalent respiratory tubes, or si- 

 phons ; r, gills ; s, foot. 



