404 



MOLLUSCA: GASTEROPODA. 



have the aperture notched, or drawn out into a canal, as 

 in Figs. 551-555. Some kinds feed upon dead animals 

 which they h'nd; others attack living mollusks, and 

 although the latter are shut tightly within their shells, 

 the hungry gasteropod, with its rasp-like tongue, files a 

 neat round hole through the shell, and then leisurely 

 leasts upon its contents. Thus clams and other large 



FIG. 540. 



Gasteropod, Littorina littnralis, removed from its shell, and the back aud 

 brauchial cavity laid open. 



r, muzzle; k, buccal mass; g, nervous ganglia; />, salivary gland; ce, oesophagus; I, 

 lingual coil; TO, shell muscle; I, branchia; c, heart; n. aorta; e, stomach; /, liver; h, 

 biliary canal; i, intestine; a, vent; o, ovary; d, oviduct; u, nidament; o, ovarian 

 orifice ; x, renal organ ; y, mucous gland. 



mollusks fall a prey even to some of the very small car- 

 nivorous gasteropods. 



