T1IK CRETACEOUS SYSTKM 465 



saurus in the Lower Cretaceous, with Acanthopholis, Anoplosaurus, 

 and others in the Upper Cretaceous. In the sea were large lizard- 

 likr reptiles of the order Squamata (Coniosaurus, Mosasaurus, and 

 Dolichosaurus), and in the air the Pterosauria were represented by 

 species of Pteranodon and Ornithocheirus. 



Remains of birds also occur in the Upper Cretaceous Series, 

 but only one genus has been found in Britain, the Enaliomis of 

 the Cambridge Greensand. In America remains are more plentiful, 

 and three remarkable genera have been described Hesperornis, 



Fig. 152. RESTORED SKEi.KTux OK HYP8ILOPHODON Koxi (h), (after O. C. Marsh). 

 Length over 5 feet. 



Ichthyornis, and Apatornis. Hesperornis was a large bird about 6 

 feet in length, and possessing many reptilian characters, so that it 

 forms a link between the Jurassic Archaopteryx and more highly 

 developed birds ; its jaws were furnished with teeth planted in a 

 long alveolar groove, its wings rudimentary, and its hind limbs 

 strong, so that it was a wader and lived chiefly on fish. Ichthyornis 

 and Apatornis were much smaller birds with well-developed wings, 

 but both had reptilian skulls with teeth set in sockets, and their 

 vertebrae were biconcave like those of Fish and Amphibians. 



Mammalia also existed, though remains of them are very rare, 

 and none have been found in England ; they consist of teeth of 



2 H 



