88 



STORY OF THE REPTILES 



head is well fitted for this, but if you will lay your 

 lower jaw on the table and open your mouth the 

 lower will not move but the whole upper jaw will 

 lift the head up and back (Fig. 46). The lower jaws 

 of reptiles are peculiar in that each side is made up 



of a great many 

 separate bones, 

 usually thou^ 

 not ajways, grown 

 together. In the 

 hither animals 

 thpTG are not so 



Sany. As noted, 

 ,e reptiles and 

 all below them 

 hang the jaw to 

 the skull by one 

 or more bones — 

 often by only 

 one, the so-called 

 " quadrate." 

 Usually this is 

 hinged or loose, 

 as in snakes and 

 most lizards ; but 

 in tortoise-forms, 

 tuatera, the crocodilians and the chameleon, it is fast 

 to the skull in various ways, of which the classifier 

 makes much. In the snakes the bone to which the 

 quadrate hangs is itself loosely hung to the side of 

 the skull, so that the jaw can be pried well away 



Fig. 46. — A crocodile {Crocodilus nilotims) 

 lying with its mouth open, showing the 

 apparent movement of the upper jaw 

 instead of the lower one. 



