FOUND LINKS. 



123 



notice of naturalists. No existing bird has teeth; 

 and no bird possesses any structures approaching 

 teeth in function save, perhaps, such birds as the 

 Mergansers, in which the horny margin of the jaw is 

 cut into a series of projections, adapted for retaining 

 a secure hold of the finny prey on which these birds 

 subsist. But in the Odontopieryx, the jaws were beset 

 with strong bony processes, which, though resembling 

 teeth in appearance, nevertheless are mere projections 

 of bone for, as most readers know, teeth are not of 

 bony nature, but possess a special and distinct struc- 

 ture of their own. Nevertheless, the fact of this 

 extinct bird of the Eocene rocks possessing toothed 

 projections of its jaws, serves to link it, in the opinion 

 of naturalists, to the reptile hosts ; for teeth are as 

 stable and characteristic possessions of the reptile 

 class as their absence is a natural feature of existing 

 birds. 



Backwards in time, and in the course of the geo- 

 logical aeons, we find the Cretaceous or Chalk rocks. 

 To the naturalist these deposits have yielded a rich 

 and suggestive harvest of bird fossils, which, in their 

 approximations to the reptiles, certainly serve as 

 " found links" in more ways than one. In the Chalk 

 rocks of North America we discover the remains of 

 1 ' toothed birds," whose teeth in every respect agree 

 with the structures of that name, and are not mere 

 bony projections, as in the old swimmer of the 

 London clay. The curious Hesperornis (see p. 60) and 

 its neighbours the Iclitliyornis and Apatornis, thanks 



