54 THE LESSON OF EVOLUTION 



Multituberculata, the teeth of which are difficult 

 to distinguish from those of the Theriodont reptiles. 

 The sub-class-, Metatheria, or Marsupials, are repre- 

 sented by the families Phascolotherida3 and Amphi- 

 therida3. In the former the lower molars have three 

 main cusps, and some accessories, all in a line ; while, 

 in the latter, the lower molars are trituberculate in 

 the anterior portion, and with one tubercule in the 

 posterior portion. Professor H. F. Osborn, how- 

 ever, includes many of these in the primitive 

 Insectivora, thus classing them with Eutherian 

 mammals. All these Marsupials belong to the sec- 

 tion called Polyprotodonta, with numerous small, 

 sub-equal, incisor teeth, and are allied to the 

 opossums, bandicoots, and native cats of Australia. 



Cainozoic Life. In comparison with the fauna, 

 the flora of the Cainozoic era is very imperfectly 

 known, owing to the difficulty of distinguishing 

 plants by their leaves only ; while their classification 

 depends chiefly on their flowers, of which very few 

 have been preserved as fossils. In the Eocene period 

 the land was either covered with forests, or else by 

 wide stretches of brown ferns , except in the swamps , 

 where rushes and other herbaceous monocotyledons 

 grew. Probably there were no herbaceous dicotyle- 

 dons until the upper Eocene. Before then the land 

 must have looked much like the north island of New- 

 Zealand at the present day, where it is untouched 

 by civilised men ; and but few butterflies and bees 

 could have existed. 



The dicotyledons are usually divided in three 

 groups : 



