64 



THE DARWINIAN THEORY 



Again, to return to biology, Phenacodus (Fig. 6), 

 one of the most important of recent fossil discoveries, 

 was found in the Eocene of North America, and in 

 several forms, varying in size from that of a small 

 terrier to a leopard. This is a good example of a 

 generalised type, having five clawed digits, a small 

 brain, and complete radius and ulna. In many ways 

 it suggests the ancestral form from which the 



Fig. 6. 



Phenacodus. 



Artiodactyla (deer and. sheep) and the Perissodactyla 

 (rhinoceros and horse) may have sprung; perhaps, 

 also, it is nearly the parent form of the Carnivora. 

 Among Birds and Reptiles a well-known series is 

 known, due to Professor Huxley, connecting the 

 one group with the other. Birds form a very 

 compact and sharply limited group, characterised 

 by their wings, feathers, and other peculiarities. 



