3S6 THE BIOLOGY OF BIRDS 



powerful hind legs well suited for energetic swimming 

 There were teeth in grooves in both jaws. A British ally 

 has received the name of Enaliornis. They probably 

 represent, as Dr. A. Smith Woodward says, " an early 

 specialised offshoot from the common ancestral type of the 

 two great surviving orders," namely, the Running Birds and 

 the Flying Birds. 



About the same time that Hesperornis swam about in 

 Cretaceous seas, like a gigantic loon, there was another 

 toothed bird, Ichthyornis victor, much smaller (towards a 

 foot high) but hardly less remarkable. It was a delicately 

 built creature, with well-developed wings and a strong keel. 

 The teeth were in distinct sockets and the vertebrae were 

 biconcave — two very striking features, harking back to 

 reptiles. But it v/as far away from Hesperornis, and was 

 definitely on the modern bird tack. Of its affinities, Mr. 

 W. P. Pycraft says cautiously, " Ichthyornis may perhaps be, 

 and generally is, regarded as the ancestral type of the present 

 Steganopodes — the gannets, cormorants, pelicans, tropic 

 and frigate birds." 



It is interesting that in Cretaceous times there should 

 have been living these two very different types — Hesperornis, 

 a specialised aquatic bird on a line pointing to divers, and 

 Ichthyornis, a flying bird, on a line pointing to solan geese. 

 There must have been many other types, some of them con- 

 necting back to Archaeopteryx, but the important fact is that 

 the modern bird type had definitely emerged. 



§ 7. Running Birds 



The flightless Running Birds or Ratitas of to-day repre- 

 sent only five genera — the African Ostrich (Struthio), the 

 South American Ostrich (Rhea), the Australasian Emu 

 (Dromaeus), the Austro-Malayan Cassowary (Casuarius), 

 and the Kiwi (Apteryx) of New Zealand. To these, accord- 

 ing to some authorities, the Tinamous should be added. 

 The persistence of the Rhea and of the Kiwi is seriously 

 threatened, and the comparatively recent extermination of 



