CLASS REPTILES. 



P 



37 



FIG. 122. Skull of rattlesnake (Crotalus durissus). From Nicholson. 

 Questions on the Figure. How much of the figure is brain-case 

 (cranium)? Which are the bones of the face? Notice how loosely 

 the bones of the jaws (ar, de, mx, etc.) are. joined to the cranium. 

 Compare the various bones with those of the fish and bird (Figs. 108 

 and 130). Study the position and articulations of the quadrate 

 bone (qu) particularly. What advantage is there in this ar- 

 rangement? Compare the quadrate in other vertebrates by ex- 

 amining figures. 



i a restoration of an extinct flying reptile. 



FIG. 123. Rhamphorkynchus m 



From the Cambridge Natural History, after Geikie. 



Questions on the Figure. In what respects does a form like this 

 differ, in external appearance, from a bird? From a bat? What 

 skeletal structures would a palaeontologist need to find in order 

 to believe that an extinct form had the power of flight? 



