92 VERTEBRA. AXr> SKULL OF THE LIZARD. 



larly completed; and then the hasmapophjses are either 

 united below without intervening sternum {chameleo\ or 

 two or three of them are joined by a common cartilage to 

 the cartilaginous end of the sternum. The hsemapophyses 

 afterwards project freely, and are reduced to short ap- 

 pendages to the pleur apophyses. These also shorten, and 

 sometimes suddenly, as, e. g. after the eighteenth vertebra 

 in the monitors (varanus\ in which they end at the twen- 

 ty-eighth vertebra, as they began, viz: in the form of 

 short straight appendages to the diapophyses. 



The flying lizard {Draco volans\ is so called on account 

 of the wing-like expansions from the side of its bod}^, sup- 

 ported, like the hood of the cobra, by slender elongated 

 ribs. In this little lizard there are twenty vertebrae sup- 

 porting movable ribs, which commence apparently at the 

 fifth. Those of the eighth vertebra first join the sternum, 

 as do those of the ninth and tenth ; the pleurapophyses of 

 the eleventh vertebra suddenly acquire extreme length; 

 those of the five following vertebrae are also long and 

 slender ; they extend outwards and backwards and sup- 

 port the parachute formed by the broad lateral fold of 

 the abdominal integuments. The pleurapophyses of the 

 seventeenth vertebra become suddenly shorter, and these 

 elements progressively diminish to the sacrum; this con- 

 sists of two vertebrae, modified as in other lizards. There 

 are about fifty caudal vertebras. 



The semi-ossified sternum in the iguana has a median 

 groove and fissure, and readily separates into two lateral 

 moieties. The long stem of the episternum covers the 

 outer part of the groove, where it represents the keel of 

 the sternum in birds. 



In the skull of the lizard order we first meet with a 

 second bony bar, diverging from the maxillary arch back- 



