156 ANATOMY OF VERTEBRATES. 



goids : these bones are applied to the back part of the tympanic, 

 and the slender ' columella ' rests upon the middle of their upper 

 surface. The parietal is perforated near its anterior border. 

 The postfrontal has a descending postorliital process. The pre- 

 frontal developes a partial post-lateral wall for the rhinencephalic 

 chamber ; externally It supports an antorbltal dermal bone : the 

 small perforated lacrymal is a distinct bone. The nasal and pre- 

 maxlllary are both single bones, as in most Lacertians. The 

 malar, wedged anteriorly between the maxillary, palatine, lacrymal 

 and ectopterygoid, curves backward as a slender style terminating 

 in a point, leaving the orbit uncircled by bone behind : the 

 squamosal, wedged behind between the mastoid and tympanic, 

 curves forward to a point beneath the postfrontal. 



In the American Monitor {Tejus nigrnpunctatus) tlie nasals are 

 divided: the malar articulates behind with the postorbital — a dis- 

 memberment of the postfrontal, which continues the zygomatic 

 arch with the squamosal : there is no ' foramen parietale.' 



In the Chameleon the teeth are short, and so confluent with the 

 jaws that these appear to have simply a serrated margin. The 

 external nostrils ])ci'forate the maxillary bone ; a long, compressed, 

 serrated crest arches upward and backward from the superocclpltal 

 and ])ariet:al bones, and joins the processes of bone continued from 

 the mastoids. In the Cliameleo bifurcus the anterior fork-like 

 productions are formed by the maxillary and prefrontal bones. 

 The premaxillary at the bottom of the cleft is -^'ery small. 



In Draco volans there is merely the rudiment of a spine or 

 ridge from the superoccipital ; an arched transverse ridge separates 

 the occipital from the parietal region of the skull. The jjost- 

 frontal, mastoid, and paroccipital project successivelv from their 

 respective cranial segments, and well manifest their character as 

 the transverse processes of these. 



The vacuities In the Ijon}^ palate are many, and show much 

 variety in the cold-blooded, especially the reptilian, series, in 

 regard to their numlier, kind, and relati\c size. The most con- 

 stant are those which are more or less circumscribed bv the max- 

 illary and pterygoid, and constitute a pair. They are present in 

 Polyj>terus and most Ganoids, l)Ounded outwardly bv the maxil- 

 lary, medially by the palatine, and behind by the pterygoid. 

 In the jMcnopome the vomer, fig. 73, /, forms the mediaV and 

 the pterygoid,/, the ]iostcrior lioundary. In the Frog, fig. OS, 

 A, the pterygo-maxillary vacuities, //, are divided from" each 

 other by the basisphenoid ; whilst the palatine forms the front 

 buundary and scjjaratcs them iVom the nasal apertures, n. In 



