208 



MULLUSlvS : CE1'HAL()I'(.)DS. 



forcibly ejecting it, they send themselves backwards 

 through the water with the swiftness of an arrow. Im- 

 mense numbers are used for bait in the cod fisheries. 

 The giant squid are related in structure to these smaller 

 ones. 



Fig. 359. — Ammonite. 



Fig. 360 — Spirula. 



Fig. 361. — Pe.irly Nautilus. Much reduced. 

 Pacific and Indian Oceans. 



