340 CLASS REPTILIA, 



supraoccipital (except in the Amphisbaenidae and chameleons), 

 but by fibrous tissue, so that the fronto-parietal part of the skull 

 is usually slightly moveable upon the occipito-sphenoidal part. 

 There is a pineal foramen either in the course of the sagittal 

 suture or between the parietals and f rentals. The parietals 

 are usually fused in the adult but remain separate in the geckos. 

 The frontals are usually paired, bat may fuse in the adult. A 

 thin splint of bone projects forwards from the basisphenoid be- 

 neath the interorbital septum (%8) ; this is a membrane bone fused 

 with the basisphenoid and representing the anterior part of 

 the parasphenoid of Ichthyopsida. The posterior part of the 

 parasphenoid is represented in the embryo by two membrane 

 bones which fuse with the basisphenoid in the adult (basi- 

 temporals). The praemaxillae are fused and there is a small 

 bone on each side just above the vomer, in the anterior part of 

 the nasal region called the septomaxillary (29). A perforated 

 lacrymal is generally present in the anterior part of the orbit. 



The squamosal (,9) is attached to the parotic process and extends 

 forward to the postfrontal (except in the geckos) forming the 

 supratemporal arcade and bounding the outer side of the supra- 

 temporal fossa (15}. The parietal sends out a postero lateral pro- 

 cess to the squamosal thus forming the posterior boundary of this 

 fossa. In most lizards the postfrontal (16) is joined to the 

 jugal (6), completing the orbit and closing the supratemporal fossa 

 in front, but in the geckos and Amphisbaenidae these bones are 

 separate and the orbit is open behind. The infratemporal arcade 

 is not developed, there being no bony connection between the 

 jugal and quadrate. The bones of the maxillopalatine apparatus 

 are firmly connected with one another and with the anterior 

 part of the skull, but the pterygoids (7) are moveably articulated 

 with the basisphenoid and quadrate. There are two vomers 

 (19) forming the inner wall of the posterior nares. The pala- 

 tines (4) pass back from these and the maxillaries to the 

 pterygoids, which diverging from one another extend back to 

 the quadrate (except in the chameleons) articulating on the way 

 with lateral (basipterygoid) processes of the basisphenoid. 

 There is a transpalatine (5) passing from the palatine and 

 pterygoid to the maxilla and jugal. In the chamaeleons the 

 supratemporals (pterotic) are much elongated and send 

 backwards and dorsalwards a process which unites with a 



