184 HALF AN HOUR WITH SHELL-FISH. 



British cuttle-fish. In the Lias formation we find 

 representatives of the modern group beginning to 

 get the upper-hand, and this dominancy continued 

 until the Nautilus family dwindled down to one 

 or two species. In the chalk formation there 

 occur an abundance of common, fossils which go by 

 the popular name of "thunder-bolts." Ignorance 



Fig. 99. 



Cuttle-fish, or Octopus. 



ascribes their origin to thunder-storms, all England 

 over. These objects, however, are nothing more or 

 less than the terminal bones of an extinct genus of 

 cuttle-fish, which was very abundant during the 

 Secondary age, but which is now extinct, and 

 represented only by the modern cuttle-fish, whose 

 bone (Sepiostaire) may be also found in some abun- 

 dance after a storm, and is made to do duty for 



