238 OUR COMMON BRITISH FOSSILS. 



world-wide character many of the same species dis- 

 tinguish Australian and American limestones and 

 shales which are characteristic of British rocks. Alto- 

 gether this is a most interesting series of animal 

 forms, and one which has played no small share in 

 the formation of the stratified rocks of the earth's 

 crust living on through long periods of geological 

 time ; silent witnesses of those great world-throes 

 and world-changes, each appearing at the time 

 destructive, but all of which were combined to make 

 our world such as we find it to-day. 



