492 



THE CRETACEOUS PERIOD 



Fig. 163. 



Skull of Agathaumas fiabellatus l from the 

 side, 1/30. (Marsh.) 



undiminished variety till the end of the Cretaceous. The erect, 

 herbivorous type is represented in these beds by Monoclonius 



and Diclonius (Fig. 

 164), which are nearly 

 related to Hadi-osaii- 

 rus . Agatha ti m a s 

 (Fig. 163) and Toro- 

 saurus are huge, quad- 

 rupedal reptiles, with 

 three large horns on 

 the head and an ex- 

 traordinary frill-like 

 extension of the skull 

 over the neck. Car- 

 nivorous Dinosaurs 

 likewise continued, such as Lailaps and Oniithomimns, the latter 

 with hind limbs which are especially birdlike in structure. 



The Birds of the Cretaceous are much more abundant and 

 advanced than the known Jurassic birds. In the Upper Creta- 

 ceous of Kansas, and 

 probably of England 

 also, are found two 

 remarkable birds, Hes- 

 peroniis and Iclithy- 

 ornis. In the former, 

 which was nearly 6 feet 

 high, the wings were 

 rudimentary, while 

 Ichthyornis, a much smaller bird, had powerful wings. Both of 

 these genera possessed teeth, like A?rh<zopteryx, but except in 

 that feature and in certain minor details of structure, they are 

 entirely like modern birds. Bird bones, like the corresponding 

 parts of the Cormorants and Waders, have been found in the green 

 sands of New Jersey, but it is not known whether they had- teeth. 

 Mammalia. — Cretaceous Mammals are much more numerous 

 and varied than those of the Jurassic, but they continue to play a 



Fig. 164. 



Skull of Diclonius mirabilis, from 

 above, 1/19. (Cope.) 



