200 REPTILIA. 



Order III. Lacertilia. — The third order of Eeptiles is 

 that of the Lacertilia, comprising all those animals which 

 are commoidy known as Lizards, together with some ser- 

 pentiform animals, such as the Blind-worms. The Lacertilia 

 are distinguished by the following characters : — 



As a general rule, there are two pairs of well -developed 

 limhs, but there may he only one pair, or all the limbs 7nay 

 be absent. A scapidar arch is always present, whatever the 

 condition of the limhs may be. An exoskelcton, in the form of 

 horny scales like those of the Snakes, is almost always present. 

 The vertebrce of the dorsal region are proccelous or concave in 

 front, rarely amphicmlous or concave at both ends. There is 

 a single transverse process at each side, and the heads of 

 tlie ribs are simple and undivided. There is either no 

 sacrum, or the sacral vertebra rarely exceed two in num- 

 ber. The teeth are not lodged in distinct sockets (som.e extinct 

 forms constituting an exception to this statement). The eyes 

 are generally furnished with movable eyelids. The heart con- 

 sists of tivo auricles and a ventricle, the latter partially divided 

 by an incomplete partiton. There is a urinary bladder, and 

 the aperture of the cloaca is transverse. 



As a general rule, the animals included under this order 

 have four well-developed legs (lig. 552), and would therefore 

 be popularly called " Lizards." In some ( Chirotcs) there are 



Fix. 552. — Itruana. 



no hind-feet ; in some (Bipes) the fore-limbs are wanting ; 

 and others (Anguis, Pseudopus, and Amphisbmna) are en- 

 tirely destitute of limbs, thus coming closely to resemble 

 the true Snakes or Ophidians in external appearance. These 



