146 



EEPTILTA 



CLASS III 



being formed by the postorbital and squamosal, and the lower arcade by 

 the quadratojugal and jugal. The latter bone is always fixed, and 

 buttressed by the pterygoids, which extend forwards to the vomer. The brain 



cavity is of small 

 size, and roofed by 

 the narrow parietals, 

 between which and 

 the pterygoids is a 

 vertical columella 

 (epipterygoid). A 

 parietal foramen is 

 generally present. 

 The paired external 

 n a r e s are almost 

 terminal in position. 

 Vomer, palatines, and 



pterygoids 



together 



form an extensive 

 bony palate. Acro- 

 dont teeth occur in 

 regular series on the 

 narrow premaxillae, 

 maxillae, and man- 

 dibles, and in some 

 cases the vomer and 

 palatines are also 

 dentigerous. Occa- 

 sionally the teeth are 

 inserted in shallow 

 alveoli, and very 

 rarelv are absent 

 altogether. 



The pectoral arch 

 is incompletely 

 ossified. The scapula is represented by an elongated rectangular bone, 

 and the inner border of the small elliptical coracoids remains cartilaginous. 

 The clavicle is a slender bent rod connecting the scapula with a large 

 rhomboidal or T-shaped interclavicle, which overlies the cartilaginous 

 sternum. The distal end of the humerus is pierced in the fossil forms by 

 an entepicondylar foramen, but in Sphenodon both entepiconclylar and 

 ectepicondylar foramina or grooves occur. In general the articular surfaces 

 of the humerus, radius, and ulna are not completely ossified. Five distinct 

 elements occur in the distal row of the carpus, and two centralia are often 

 present. The extremities are pentadactylate. 



The pelvic arch consists of a small, nearly vertical ilium, a discoidal pubis 

 with obturator notch, and a somewhat expanded ischium, which remains 

 separated from the pubis. Both pubis and ischium are imperfectly ossified 

 among the earlier forms. The hinder is somewhat longer than the fore-limb, 

 and resembles that of Lacertilians and Theromorphs. 



Fig. 237. 



Sphenodon punctatus, Gray. Recent; New Zealand. Lateral, palatal, 

 posterior, and superior aspects of skull. ~/ 3 . (A, Orbit; ang, Angular; art, 

 Articular; bo, Basioccipital ; eh, Internal nares ; d, Dentary ; ceo, Exoccipital ; 

 r, Frontal ; ju, Jugal ; k, Surangular ; mx, Maxilla ; N, External narial opening ; 

 na, Nasal ; opo, Opisthotic ; pa, Parietal ; pi, Palatine ; pmx, Premaxilla ; por, 

 Postorbital; prf, Prefrontal; pt, Pterygoid ; ptf, Postfrontal; >ju, Quadrate; 

 QVJt Quadrato -jugal ; S, Supratemporal vacuity; so Supraoccipital ; sq, 

 Squamosal ; vo, Vomer.) 



