XI 



PHYLUM MOLLUSCA 



299 



of either eight or ten long, highly extensible and contractile 

 appendages, the arms, the inner surfaces of which are beset 

 with numerous suckers, rendering them powerful grasping 

 organs. These are arranged in a circlet surrounding the 

 mouth. The posterior part of the foot appears to be repre- 

 sented by the funnel, a wide tube through which water is 



ch" 



FIG. 184. Section of the shell of Nautilus pompilius, showing the septa (s, s), the 

 septal necks (s. ., s. .), the siphuncle (si, represented by dotted lines), and the 

 large body-chamber (ch}. (From the Cambridge Natural History.} 



driven out from the mantle-cavity. In the Nautili (Fig. 183), 

 (sub-class Tetrabranchiata), the place of the arms with their 

 suckers is taken by a number of lobes bearing sheathed 

 tentacles surrounding the mouth, and a funnel is also pres- 

 ent, though it does not form a complete tube. 



'si 



