ANCIENT BIRDS 229 



back, the geological record informs us that, in the Pliocene 

 period, they inhabited what is now Northern India. In Australia 

 we have the Cassowary (Casuarius) and the Emeu (Dromaius) ; 

 in New Zealand, the Apteryx (or Kiwi). Now, as none of these 

 birds can either fly or swim, it is impossible that they could 

 have reached these regions separated as they now are; and it 

 is hardly likely that they arose spontaneously in each district 

 from totally different ancestors. But the doctrine of evolution 

 affords a key to the problem, and tells us that they all sprang 

 from a common ancestor, of the struthious type (probably 

 inhabiting the great northern continental area), and gradually 

 migrated south along land areas now submerged. In this way 

 we get some idea of the vast changes that have taken place in 

 the geography of the world during later geological periods. 

 Perhaps they were compelled to move south, until they reached 

 abodes free from carnivorous enemies. Having done so, they 

 evidently flourished abundantly, especially in New Zealand, where 

 there are so few mammals, only those recently introduced by 

 man. 



In North America Professor Cope has reported a large wingless 

 fossil bird from the Eocene strata of New Mexico. In England 

 we have two such namely, the Dasornis, from the London Clay 

 of Sheppey (Eocene period), and the Gastornis, from the Wool- 

 wich beds near Croydon, and from Paris (also Eocene). 



Lake Callabonna in Australia (see p. 310) has yielded the bones 

 of some huge ratite birds, e.g. G-enyornis, with very slender toes. 

 It lived with the Diprotodon. In South America the living 

 Ptheas were preceded by such large birds as Brontornis, of 

 which casts of limb-bones are to be seen in the Natural History 

 Museum. The famous Sivalik strata of India have yielded 

 remains of an ostrich, Struthio asiaticus, and these may be seen in 



