THE ALIMENTARY CANAL. 



81 



Fio. 45. Anatomy of a Gasteropod (Snait): a, month ; &, foot; c, anus; d, lung^ 

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

 i, aorta; j, gastric artery; Z, hepatic artery; k, artery of the foot; w, 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. 4 * Indeed, it is common for 



q 



8 I k r b 



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



lips; rf, mouth; e, nerves; /, muscles; g, anterior, and n, posterior ganglion ; h, 

 liver; t, heart: k, stomach ; I, intestine passing through the heart; w, kidney; o, 

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

 phons ; r, gills ; , foot. 



6 



