Guide to the Invertehrata. 



Nautilus, through which the water from the mantle or gill-chamher is 



GALLERY forcibly ejected, propelling the animal backwards with rapidity 



through the water. 

 Wall -case 

 la. 



Fig. 18. 



-Shell of the Pearly Nautilus, Nautilus pompilms, Linn. 

 Indian Ocean. (Reduced.) 



All the Cephalopoda are marine and predaceous animals, living 

 on other mollusca, crabs, and fishes, and possess considerable powers 

 of locomotion. At the bottom of the sea, and in the rocky pools 



Fig. 19. — Animal of the Pearly Nautilus in its shell. (The shell is cut open.) 

 c, the mantle ; b, the dorsal fold of mantle ; ff, shell-muscle ; 

 i, i, siphuncle ; k, funnel ; n, hood ; p, tentacles ; «, eye ; x, x, the 

 septa ; z, last chamber. (Reduced.) 



along the shore, they can crawl about head downwards, by means 

 of the tentacles, or feet which surround the mouth, and which 

 are usually furnished with numerous suckers or acetahula. They 

 are also able to swim, partly by means of lateral expansions of 



