SAURIAN REPTILES. 457 



4. Sauria. 



THE conformation of those parts of the frame 

 which are subservient to progressive motion 

 becomes more perfect in the class of Saurian 

 reptiles, which includes all the Lizard tribes. 

 Several links of connexion with the preceding 

 class may still be noticed, marking the progress 

 of developement, as we follow the ascending 

 series of animals. Rudiments of the bones of 

 the extremities, and also of the sternum make 

 their appearance very visibly in the Ophiosaurus, 

 and in the blind worm (Anguis fragilis). The 

 Siren lacertina has two diminutive fore feet, 

 placed close to the head. The Lacerta lumbri- 

 coides of Linneus, or the Bipes canal iculatus of 

 Lacepede, which is found in Mexico, and of 

 which a specimen is preserved in the collection 

 at Paris, has a pair of very short feet, also placed 

 near the head, and divided into four toes, with 

 the rudiment of a fifth. The Lacerta bipes 

 (Linn), or Sheltopusic of Pallas, has, on the 

 other hand, a pair of hind feet only, but ex- 

 tremely small, together with rudiments of a 

 scapula and clavicle concealed under the skin. 

 Next in order must be placed the Chalcides, 

 or Snake-lizard (Fig. 210), and the Lacerta 



