EVIDENCE FROM PALAEONTOLOGY 91 



pods were less abundant and varied than in the 

 Cenozoic, the beautiful chambered shells called Am- 

 monites were incredibly numerous and diversified. 

 In the successive forms of these shells many 

 striking genealogical series have been made out. 

 The curious Belemnites are almost exclusively 

 Mesozoic. 



In all the recorded history of life there was no such 

 radical and far-reaching revolution as that between 

 the Palaeozoic and Mesozoic eras. Could a naturalist 

 be transported into the former he would find him- 

 self in an unfamiliar world, in which almost every 

 animal and plant that he saw would be strange to 

 him. The land vegetation was made up of gigantic, 

 tree-like cryptogams, especially the lycopods and 

 horse-tails, and the abundant ferns were both in 

 arboreal and herbaceous forms. The flowering plants 

 were represented but scantily and by curious trees 

 allied to the cycads and conifers, but of such plants 

 in the ordinary use of the word, there was no trace, 

 nor was any mammal or bird in existence. The vast 

 majority of Palaeozoic fossils belong to marine in- 

 vertebrates, for, except in the latter part of the era, 

 the only vertebrates were fishes and fish-like forms, 

 sharks, ganoids, lung-fishes and certain bizarre, 

 mailed animals, which were below the fishes in the 

 scale of organization. The seas were swarming with 

 a profusion of invertebrate life, many of which, 

 though referable to types and classes which are still 

 existing, were much more primitive in structure 



