5 i8 



THE ARCH&OPTERYX. 



not always, have the cup in front and ball behind, as in living croco- 

 diles and most lizards and all serpents, but all the other bones are 

 bird-like in their plan. The wing is only comparable with the wing 

 of a bird, though a digit was elongated to stretch the wing membrane 

 to the same area as feathers extend the wing of the bird. Ornithosaurs 

 could walk on two feet or four feet, but most were aquatic animals, 

 probably divers, living on fish. Air-chambers prolong the breathing 

 organs into the limb bones, as in living birds. The English genera are 

 JJimorpJtodon in the Lias, Rhampliorhynchus and Dolicorhampkus in 

 the Stonesfield slate ; some Pterodactyles occur in the Kimmeridge 

 clay. Doratorhynchus is a genus of the Purbeck beds, and Ornitho- 

 cheirus, distinguished by having prehensile teeth directed forward 

 from the front of the snout, ranges from the Wealden beds to the 

 Chalks, and is especially numerous in the Cambridge Greensand. 

 Omithocheirus probably had but three digits in the fore-limb. 1 The 

 Ornithosaurs include the Pterodactylia and Pterosauria. 



Aves. Birds have been divided into three groups : Saururise, in- 



C. 



Fig. 146. Head of Archaeopteryx. 



A. orbit; B. ant-orbital vacuity ; C. external nasal aperture ; *cl. sclerotic circle ; p.f. frontal 

 bones; n. nasal bones; im. premaxillary ; I. lachrymal; m. maxillary; p.p.nt. palatine 

 plate of the maxillary ; p. palatine bone ; pt. pterygoid bone ; qu. quadrate bone ; mi. 

 lower jaw ; p.pa. post articular process of the mandible ; h. hyoid bones. 2 



dicated by the Archaeopteryx ; the Ratitae, including all Struthious 

 birds ; and Carinatae, which comprise birds of flight. 



The Archseopteryx is remarkable for having the skull formed upon 



1 See Ornithosauria. 8vo, 1870. Jour. Linn. Soc. Zool., vol. xiii. Annal< 

 Nat. Hist., Jan. 1871. 



- See W. Dames : " Ueber Archaeopteryx, Palaeontologische Abhandlungen, 

 Zweiter Band," Heft 3, Berlin, 1884, for an admirable discussion of this fossil, and 

 an excellent figure. See also R. Owen : Phil. Trans. Royal Soc. 1863. 



