BELEMNITES. 281 



an iutemal coiled shell. The shells of S2)irula Peronii La- 

 marck are rarely thrown ashore on Nantucket ; it lives u]3on 



Fig. 222. — Pearly Nautilus, iV. pmnpiliufi. Seen in section Bhowing 

 the chambers and siphuacle. Half natural size. — From Tenney's Zo- 

 ology. 



the high seas. The extinct Belemnites was provided with an 

 air-cavity (phragmocone) with a straight shell, the " thunder- 



Pig. 223.— Pouipe or Common Octopus of Brazilian Coast. 



bolt" fossil. Allied to Loligo and Om mast replies, are gigan- 

 tic cuttle-fishes which live in mid-ocean, but whose remains 



