THE ANATOMY OF THE LIZARDS 21 



watched in the living Z. agilis and viridis, and in 

 these animals also the fresh skull was examined in 

 order to discover the possibilities of movement between 

 the various parts." 



It was long ago pointed out that the movements 

 of the jaws in lizards did not consist merely in the 

 depression and elevation of the lower jaw, but that 

 there was along with this a corresponding elevation 

 and depression of the upper jaw. This movement of 

 the upper jaw was supposed to take place along two 

 lines — first, between the frontal and parietal bones; and 

 second, between the parietal bones and the occipital. 

 Dr. Bradley comes to a different conclusion. " It 

 may be stated at once that the anterior line of 

 movement, as described by Nitzsch, does not exist. 

 The joint between the frontal and parietal bones is 

 not movable. Certainly, in the skull of a lizard, such 

 as L. viridis, a certain bending can be produced, 

 but it is dependent upon the thinness of the bones, 

 and not upon any peculiarity in the line of fusion of 

 frontal and parietal bones. In the larger lizards, and 

 in those with thicker cranial bones, such a bending is 

 not possible unless extreme force is used." ..." The 

 two halves of the mandible are very loosely joined 

 together at the symphysis. It appears not unreason- 

 able to expect that in the living animal there is some 

 degree of rotation of each half of the mandible about 

 its own long axis. Such rotation, at any rate, can 

 be very readily produced in a fresh skull," 



