THE SKELETON. 215 



carry the body raised from the ground ; but in locomotion are used 

 principally for pushing the body forward ; they may also be used for 

 clinging (Chamselion), climbing (Geckos), and digging. They usually 

 end with five clawed digits. They are sometimes so short and rudi- 

 mentary, that they have the appearance of stumps applied to the 

 serpent-like body, and are without separated digits (Chamcesaura). 

 In other cases rudiments of the posterior limbs alone exist (Pseudopus) 

 (fig. 641), or anterior limbs only are present (Chirotes) ; or finally 

 external limbs may be entirely absent (Anguis, Acontias, 0-phi- 

 saurus). The pectoral and pelvic girdles are however present, and 

 in all Lizards except Amphisbcena there is at least a rudiment of 

 the sternum, which increases in size as the anterior limbs become 

 more developed, and then serves for the attachment of a correspond- 

 ingly greater number of ribs. The ribs are only wanting on the 

 most anterior cervical vertebrae, and sometimes on some of the 

 lumbar as well as on the caudal vertebrae. The anterior ribs present 

 a peculiar modification in Draco, being extremely long and serving 

 to support lateral expansions of the skin, which can be used as wings. 



The cranial capsule (fig. 631) does not usually extend into the 

 orbital region, behind which it is imperfectly closed by membranous 

 structures (membranous interorbital septum). The squamosal is 

 firmly attached to a strongly projecting process (parotic process) of 

 the posterior\ temporal region. The hinder end of the maxilla is 

 frequently connected with the postfrontral (Pf) by a bony bridge, the 

 jugal (fig. 631 J), which encloses the orbit ; while a bone (quadrato- 

 jugal) passes from the jugal to the quadrate, bridging over the 

 temporal region. 



An important character of the Lizards as opposed to the Snakes 

 consists in the fact that the bones of the jaws are not movable upon 

 one another. Parts of the maxillo -palatine apparatus are indeed 

 movably connected with the skull (Hatteria = Sphenodon excepted), 

 especially the pterygoids, which are applied to the articular processes 

 of the basisphenoid, and usually articulate with the quadrate ; but 

 the individual bones of the maxillo -palatine apparatus are firmly 

 connected with one another, and with the anterior part of the skull. 

 The pterygoids are firmly attached to the maxillaries by a transverse 

 bone, and serve to support the parietal bones by a rod-shaped 

 columella [a bone which extends from the parietal to the pterygoid 

 on each side]. On the top of the skull the parietal bones and the 

 occipital segment are connected by fibrous tissue, and in consequence 

 are slightly movable upon one another. The quadrate bone is 



