1 3 o OUR COMMON BRITISH FOSSILS. 



CHAPTER V. 



FOSSIL STAR-FISHES AND SEA-URCHINS. 



LET me next call attention to the commonest fossils 

 belonging to the Star-fish and Sea-urchin family. 

 Few fossils have a more attractive aspect than they, 

 and none exceed them in the singular beauty of their 

 structures, and their marvellous adaptation to their 

 ancient habits of life. 



Now that we have got rid of the useless term 

 Radiata and are beginning to arrange animals in 

 their natural relationship to each other, we have 

 learned comparative zoology. To this most interest- 

 ing study the whole science of palaeontology or that 

 which deals with the extinct life of our globe con- 

 tributes equally with zoology. In surveying such a 

 large natural group as that formed by the annuloid 

 animals, we are frequently surprised by the singular 

 way in which otherwise extreme types spring from 

 almost common or neutral ground. Thus, the extinct 

 groups of Cystideans and Pentremites, peculiar to 

 the Palaeozoic rocks, and which severally represent 



