358 HISTORICAL GEOLOGY. 



Toothed-birds, wholly different from anything now living. 

 These Toothed-birds were, again, of two types. Those 

 of the one class (of which the Hesperornis may be taken 



FIG. 322. Ichthyornis victor, x . FIG. 323. Hesperornis regalis, x T V (Re- 



(Restored by Marsh.) stored by Marsh.) 



as a type) were flightless swimmers and divers, of great 

 size (five to six feet long), with scarcely a rudiment of 

 wings. Those of the other class (of which the Ichthy- 

 ornis is the type) were smaller in size, hut powerful fliers. 

 The Hesperornidw had teeth in grooves a lower condi- 

 tion. The IclithyornidcB had teeth set in distinct sockets. 

 We give herewith (Figs. 322, 323) Marsh's restorations of 

 these two types. 



Mammals. We found marsupials somewhat abundant 

 in the Jurassic, though no true typical mammals. It is, 

 therefore, somewhat remarkable that no mammal of any 

 kind has yet been found in the Cretaceous, except in the 

 Laramie, which may be regarded as a transition to the 



