or Toothed Birds of North America. 273 
ee 
Odontornithes as a sub-class, and to separate them into three 
each other. The free metacarpals and long tail of Archeopteryx 
are significant characters. Gegenbaur and Morse, however, 
have shown that young birds of existing species have the 
metacarpals separate, and this is true for all these birds up to 
4 certain age. Hence this character is of less importance than 
the presence of true teeth, since in no recent birds, young or 
old, have these been found. The length of tail is perhaps a 
character of more value, but this is a variable feature in 
modern birds. 
Sub-class ODONTORNITHES (or Aves Dentata), Marsh. 
Order, OpoyroLom, Marsh, |ODONTOTORM#, Marsh. |SauRUR&, Heckel. 
Genus, Hesperornis, Marsh. Ichthyornis, Marsh. Archeopteryx, von Meyer, 
: . Teeth in sockets Teeth i ? 
r Wer jaws separate. Lower jaws separate. |Lower jaws ? 
katie saddle-shaped. Vertebree biconcave. ertebrz ? 
Met rudimentary. Wings large. Win 
- etaca s wanting. Metacarpals ankylosed.|Metacarpals separate. 
Sternum without keel. Sternum with keel. | /Sternum ? 
ail short. Tail short. Tail longer than body. 
: “That the three oldest known birds should differ so widely 
x Ng — other points unmistakably to a great antiquity for 
€ class, E 
reptilian features. For the primal forms of the bird-type, we 
Must evidently look to the Paleozoic; and in the rich land 
una of our American Permian we may yet hope to find the 
remains of both Birds and Mammals. 
‘The genera Archeopteryx, Hesperornis and. Ichthyornis, each 
Possessed certain generalized characters not shared by the 
others. These characters were undoubtedly united in some 
