THE SKULLS OF REPTILIA AND AYF.S. 



231 



mental modification, the proximal end of that bone being 

 originally in Ophidia, as in other Reptiles, applied to the 

 periotic capsule. 



The palatomaxillary apparatus presents a considerable 

 diversity of structure in Keptiles and Birds. In all Birds, and in 

 most Reptiles, the pterygoid and the quadrate bones are more or 

 less closely connected, but in the Crocodiles and Chamseleons 

 they are separated. In Crocodiles and CheIo?ua, and in the 

 extinct Plesiosauria, the quadrate bone is immoveably united 

 with the skull, and the other facial bones are firmly and fixedly 

 united with one another and with the cranium. In most Birds 

 and Lacertilia, on the contrary, the quadrate bone is moveably 



Fig. 94. 



Fig. 94. — Views of one half of the palatine surface of the skull of, A, a Lizard (Cyclodus), 

 and B, a Turtle (Chelone midas). N\ the posterior nasal aperture. 



articulated with the skull, and its motion may be communicated 

 by the pterygoid, the quadrato-jugal and the jugal bones to the 

 fore-part of the face. This mobility reaches its maximum, on 

 the one hand, in such birds as the Parrots, in which the beak 

 and fore-part of the basi-facial axis are united by a sort of hinge 



