ORDER ORNITHOSAURIA. 



197 



yet revealed to us. So strange, indeed, are they that some autho- 

 rities have considered that the 

 Ornithosaurs are entitled to rank 

 as a distinct class ; but they are 

 essentially Reptiles, and agree in 

 their intrinsic characters with the 

 other two orders placed in the 

 branch now under consideration. 

 All their organisation is, however, 

 modified for the purpose of flight 

 through the air. Thus the body 

 was supported during flight by a 

 membranous expansion, or pata- 

 gium^ which was mainly borne by 

 the greatly elongated phalangeals 

 of the ulnar, or outermost digit of 

 the manus (fig. 1095, marked iv) ; 

 but which also extended along the 

 sides of the body to embrace the 

 hind limbs and tail (fig. 1098). 

 The vertebrae are proccelous, and 

 have their neuro - central suture 

 obliterated ; the precaudal series 

 is not numerous ; the cervicals are 

 longer than the dorsals • and from 

 three to six vertebras are anchy- 

 losed together to form the sacrum. 

 The cervical ribs in those cases 

 where they have been observed 

 are of the Crocodilian type. The 

 skull (figs. 1096, 1097) is rela- 

 tively large ; and although more 

 or less bird-like in general con- 

 tour, yet maintains the reptilian 

 type by the presence of the supra- 

 temporal fossae, bounded by the 

 junction of the postorbital with the 

 squamosal bone. Bird-like resem- 

 blances are, however, shown by 



the Circumstance that the bones Of Scaphognathus crassirostris ; B, Sternum 



, in ii 1 i and coracoids of Ptcrodactylus. h, Hu- 



the Skull anchylOSed together at merus; r, Radius; u, Ulna; c, Carpus; 



an early age ; and that the two Sd^' These sh ° uld haVe ^ """ 

 rami of the mandible were com- 

 pletely welded together at their symphysis. Moreover, as in Birds, 

 the greater portion of the upper jaws is formed by the premaxillae ; 



