22 BRITISH LIZARDS 



After describing in detail the movements of the 

 different segments of the skull, Dr. Bradley sums 

 up the effect of these movements thus : " Least 

 movement occurs in the neighbourhood of the ends of 

 the projecting lateral occipitals, in which region, it 

 may be remarked, are the upper ends of the quadrate 

 bones. There is elevation of the frontal segment at 

 the same time as the mandible is depressed, and 

 at the same time there is a narrowing of the mouth, 

 which narrowing is greatest posteriorly. When the 

 mouth is closed, the parts are restored to the condition 

 of rest, i.e. there is depression of the frontal segment, 

 and abduction of the pterygo-palatine arch, lower end 

 of the quadrate and posterior part of the mandible. 

 This results in an increase in the transverse diameter 

 of the mouth, the increase being greatest posteriorly. 

 If the frontal segment be more forcibly depressed, the 

 basipterygoid processes of the sphenoid exert their 

 wedge-like action upon the pterygoid, so producing 

 further abduction. Therefore, when the frontal segment 

 is depressed, the transverse diameter of the mouth is 

 increased. 



" The advantage of the abduction and adduction of 

 the jaws is obvious when we remember the nature and 

 condition of the food of lizards. Their prey is always 

 living, and therefore we may presume desirous of 

 escape. Supposing the victim to be a worm, the fol- 

 lowing is apparently the manner in which the lizard 

 succeeds in swallowing it. From its conformation the 



