220 THE ANATOMY OF VEETEBRATED ANIMALS. 



parietal to the pterygoid on each side, in close contact 

 ■with the membranous or cartilaginous wall of the skull. 

 Hence they hare been called " Kionocrania," or " column 

 skuUs." This columella (Fig. 69, Co) appears to correspond 

 with a small independent ossification, which is connected 

 with the descending pi-ocess of the parietal and with the 

 pterygoid, in some Chelonia. 



In the gi-eat majority of the Lacertilia (as in the Chelonia), 

 the side-walls of the skull, in the region of the ear, are pro- 

 duced into two broad and long parotic processes, into the 

 composition of which the opisthotic, ex-occipital, and pro- 

 otic bones enter. Each quadrate bone is articulated with the 

 outer end of one of these processes (in which a smaU separate 

 pterotic ossification sometimes appears), and is usually move- 

 able. The parietal bones do not unite suturaUy with the occi- 

 pital segment of the skuU, or with the pro-otic bones, but 

 are connected with them only by fibrous tissue. And as the 

 presphenoidal region remains unossified, or incompletely 

 ossified, it follows that the f ronto-pai ietal portion of the 

 skxill is, in most Lizards, slightly moveable upon the occi- 

 pito-sphenoidal part. 



Each parietal bone is prolonged backwards into a process 

 which articulates with the upper part of the parotic pro- 

 longation of the skull ; and to the outer side of the posterior 

 extremity of the parietal process the squamosal is attached. 

 The squamosal may he continued forward to the post- 

 frontal, which is sometimes subdivided into two. The post- 

 frontal may unite below with the jugal, and thus bound the 

 orbit. Only in Sphenodon, among recent Lizards, is the 

 jugal connected with the distal end of the quadrate by 

 bone. As a general rule the quadrato-jugal is represented 

 only by a ligament. 



In consequence of the structure which has been described, 

 the posterior region of the ordinary Lacertilian skull pre- 

 sents a number of distinct fossae in the dry state. A supra- 

 temporal fossa lies between the parietal, the postfrontal, 

 and the squamosal, on the upper face of the skuU ; apost-tem- 

 poral, between the parietal, the occipital, and the parotic 



