THE EVOLUTION OF MAN 



birds are merely a side line of the great main 

 branch of reptiles. 



Nevertheless, during this typical saurian age, 

 there already existed some mammals, as is proved 

 by the remains of their bones. True, they do 

 not seem to have played a very prominent role. 

 Their remains have been found, therefore, only 

 in a few portions of the secondary strata. And 

 all these scant remains belong to rather small 

 animals, but such as they are they are well pre- 

 served and teach us an important lesson. 



In our transition from the Tertiary period 

 backward into more primitive times, we become 

 aware of the fact that all higher mammals gradu- 

 ally disappear, even that archetype of Cernays 

 and New Mexico. Instead of them, the remains 

 of mammal bones, wherever they may appear, be- 

 long to representatives of a certain group of 

 lower mammals, the so-called marsupials. / 



The best known type of marsupial is the kan- 

 garoo. But there are still a number of other rep- 

 resentatives living, most of them in Australia, 

 some of them also in America. These marsupial? 

 have, among other peculiarities, a bony projec- 

 tion in their lower jaw, and this always distin- 

 guishes their jaw from that of any other 

 mammal. The fossil lower jaws of these second- 



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