ORDER II 



SQUAMATA 



161 



dorsal ribs which join the sternum are sometimes cartilaginous, and in other 

 cases bony. 



The skull (Fig. 253) is distinguished from that of Rhynchocephalians 

 chiefly by its large free quadrate, a delicate rod-like columella, and the con- 

 stant absence of a lower and occasional absence of an upper temporal arcade. 



Qu.] 



Fig. 253. 



Monitor nüoticus, Hassl. Recent ; Egypt. Skull, lateral aspect, i/i- (eol, Columella or epipterygoid ; cm, 

 Exoccipital ; fr, Frontal ; ju, Jugal ; la, Lachrymal ; mx, Maxilla ; N, Narial opening ; na, Nasal ; pa, Parietal ; 

 pl, Palatine ; pmx, Premaxilla ; prf, Prefrontal ; pro, Proötic ; pt, Pterygoid ; ptf, Postfrontal ; qu, Quadrate ; 

 (luj, Quadrato-jugal ; S, Supratemporal vacuity ; so, Supraoccipital ; sq, Squamosal ; t, Transverse bone or ecto- 

 pterygoid ; y, Öuperciliary), (after Cuvier). 



The vomer is unpaired, and not in contact with the pterygoids ; and the 

 latter, together with the palatines, form a fiat thin palate pierced by large 

 vacuities. A transverse bone (ectopterygoid) occurs between the maxillae 

 and pterygoids. The external nares are separate, and commonly placed near 

 the Orbits. The opisthotic is fused with the exoccipital, forming the so-called 

 parotic process of the posterior temporal region. The distal end of this 

 process serves with the posterior ends of the squamosal and prosquamosal as 

 a buttress to which the movable quadrate is attached. The squamosal itself 



Fig. 254. 

 Iguana tuberculata, Laur. Recent ; West Tndies, Inner aspect of right ramus of mandible, showing pleuro- 

 dont teeth. (ang, Angular ; art, Articular ; d, Dentary ; k, Coronoid ; op, Splenial ; s.ang, Surangular), (after 

 Cuvier). 



is of small size and situated between the outer angle of the parietal and 

 distal end of the prosquamosal. The postorbito- frontal unites with the 

 forward end of the prosquamosal to form the lower border of the superior 

 temporal fossa, and also unites with the jugal to form with this bone the 

 posterior border of the orbit. In lizards the jugal is never in direct connec- 

 tion with the quadrate. A parietal foramen occurs, and the parietal is 

 frequently unpaired. 



The mandibular rami (Fig. 254) are suturally united at the Symphysis ; 

 they exhibit the same structure as in Pythonomorphs, except that there is no 

 movable articulation behind the middle of each ramus. Teeth are always 

 VOL. II M 



