496 LACERTILIA 



CHAP. 



bending of the foot is effected Ity truly intertarsal joints. The 

 greatest modification occurs in the foot of the Chameleons, in 

 which the proximal tarsalia are reduced in number, and form a 

 globe for the articulation with the tibia and fibula. 



The shoulder-girdle and sternum much resemble that of Sjiheno- 

 don in their completeness. The coracoids articulate with the 

 sternum ; the precoracoids and the basal parts of the scapulae 

 often send out several processes towards those of the other side, 

 so that several fenestrae are formed. The clavicles are complete, 

 Ijut are absent in the Chameleons. The interclavicle is mostly 

 T-shaped. A presternum is absent, but the sternum proper is 

 well developed, often forming a rhomboid plate, usually carti- 

 laginous, often diverging backwards into xiphisternal processes. 



The pelvis is attached to two vertebrae by means of several 

 ribs. The ischium and pubis form symphyses. The pubis 

 carries a well-developed lateral process, and the obturator-nerve 

 pierces the shaft of the pubis. Epipubic and hypo-ischial 

 cartilages are of frequent occurrence. 



The hyoid apparatus consists of a median, styliform rod, 

 which extends forwards into the tongue ; it is often bifid 

 behind. The unpaired piece carries two pairs of horns. The 

 posterior of these, the first pair of branchial arches, extends 

 backwards along the gullet, and is very long if the tongue is very 

 slender and protractile. The anterior pair, the hyoid arches, 

 consists of two pieces on either side, one short and directed 

 forwards, the other long, connected with the former at a sharp 

 angle and continued upwards to the sides of the skull, often in 

 direct continuity with the columellar chain of the ear. 



The modifications of the skull concern chiefly the composition 

 of the temporal arches, see Figs. 55, M, N, 0, p. 281. The 

 quadrate bone is movable, but it has become fixed in various 

 degraded families, where the skull shows a great reduction 

 and concentration ; the postorbital and temporal arches, the 

 interorbital septum, and with it the columellae cranii are lost. 

 The columella cranii of the Chameleons, which is generally stated 

 to be absent, is really present, although in a much reduced state, 

 and is partly imbedded in the interorbital septum. The occipital 

 condyle has become bifid in Amphisbaenidae. 



Burrowing and living in sand are often correlated with 

 partial or complete reduction or loss of the limbs and their 



