304 OUR COMMON BRITISH FOSSILS. 



second, those which had hard internal structures, like 

 those represented in the Secondary rocks by the 

 numerous Belemnites, and in modern seas by the 

 " cuttle-bones." 



The lovely shell of the modern striped Nautilus 

 pompilius is well known, and may be seen in any 



Fig. 302. Internal shells of recent Cuttle-fish. 



museum. Its architectural and mechanical structure 

 appears to be the same nowadays as it was in the 

 early Palaeozoic ages of the globe. There is a series 

 of chambers united by a tube called the siphuncle 

 running through the centre of them. The last 

 chamber is the largest, and is called the body-chamber, 

 because it was last occupied by the body of the 



