66 THE OSTEOLOGY OF THE REPTILES 



acrodont or pleurodont; the prearticular of the mandibles is always 

 fused with the articular. Other characters are very variable in this 

 extensive order, which is sometimes divided into two or three dis- 

 tinct orders. 



Sauria or Lacertilia 



In the lizards (Figs. 55, 56) the quadrate articulates above nor- 

 mally with three bones, the squamosal, paroccipital, and a third 

 bone whose homology is yet disputed, but which is usually called 

 the supratemporal. The squamosal may be absent in those lizards 

 without a temporal arch, and rarely in certain degraded burrowing 

 lizards (Fig. 56) the "supratemporal" may also be absent, the 

 quadrate lying against the brain-case and more or less fixed by the 

 pterygoid. The paroccipital usually but not always helps support 

 the quadrate. 



As regards the identity of all these bones, there has been great dif- 

 ference of opinion, and there is by no means unanimity at the present 

 time. The tabular, as here identified, has been called the squamosal, 

 supramastoid, supratemporal, and even the paroccipital (opisthotic). 

 The squamosal as here considered has been called the quadratojugal, 

 supratemporal, paraquadrate, squamosal, and prosquamosal. The 

 reasons for their identification as the tabular and squamosal will be 

 found in the discussion of the skull of the Protorosauria. 



Below, the quadrate articulates with the pterygoid on the inner 

 side by a rather free joint in most lizards, in some, like the Am- 

 phisbaenia (Fig. 56) by a close sutural joint. On the inner side the 

 usually slender stapes abuts against the quadrate (Fig. 55 c). In 

 the mosasaurs there is an elongated suprastapedial process arching 

 backward and often extending to the lower end, enclosing the au- 

 ditory meatus, as in some turtles. 



The tabular (Fig. 55 a, to), or supratemporal, at the distal and 

 under side of the parietal process, forming more or less of the boun- 

 dary of the temporal opening, articulates with the squamosal, par- 

 occipital, and quadrate. In the mosasaurs (Fig. 54 c) only, it has 

 a long internal process, firmly wedged in between the paroccipital 

 and prootic, extending nearly or quite to the semicircular canals. 

 In some lizards the tabular has suffered reduction or has become 

 indistinguishably fused with the squamosal. 



