CRETACEOUS ANIMALS. 



491 



nary combination of bird characters with reptilian and fish characters. 

 So extraordinary and exceptional is this combination of characters, 



Fig. 825.— Hesperornis regalis, x T V (restored by Marsh). 



that Marsh believes he is justified in placing them not only in new 

 orders, but even in a new sub-class. According to this authority, the 

 class of Birds may be divided into two sub-classes, viz., Omithes, or 

 true birds, and Odontomitlies, or toothed birds. And the new sub- 

 class Odontornithes into three orders, viz. : (1) Saururce (reptile-tailed), 

 represented by the Archaeopteryx, (2) Odontolcce (teeth in grooves), 

 represented by the Hesperornis, and (3) Odontotomies (teeth in sock- 

 ets), represented by the Ichthyornis. Yet, exceptional as these char- 

 acters may seem, they are just what the law of evolution would lead us 

 to expect in the earliest birds. As already stated (p. 455), this branch 

 had not yet been fairly separated from the reptilian stem. It is a 

 noteworthy fact that these toothed birds lived at the same time and 

 in the same localities with the toothless Pterosaurs mentioned on 

 page 486. 



It is a remarkable fact that in the earliest representatives of each 

 class the brain is relatively very small. This is true of reptiles, birds, 



