LIZARDS. 67 



*'The passage from the Lizard tribe to the 

 Serpents," observes Mr. Bell, "is by a succession 

 of very gradual modifications of development. In 

 the lower forms of the Saurian group, the body 

 becomes gradually elongated and serpentiform : 

 its ribs increase in number, the anterior and pos- 

 terior hmbs are removed farther and farther from 

 each other, and diminish in size and power, ex- 

 hibiting in some forms the anterior, and in others 

 the posterior only, external to the integument, 

 until at length they cease to appear, being merely 

 rudimentary, and wholly covered by the skin. 

 Of this transition state we have an example in 

 the common Slow-worm {Anguis fragilis), which, 

 though completely serpentiform in its external, 

 appearance, yet possesses the minute rudiments 

 of limbs entirely concealed under the integuments. 

 Notwithstanding this general form of the Serpent, 

 they have not the expansible jaws of the true 

 Serpents : nor is the character of the ears the 

 same, the tympanic membrane not being superficial, 

 nor the auditory passage covered by integument ; 

 the eyes, also, like those of the Lizards, are fur- 

 nished with moveable eyelids, which are wholly 

 wanting in the true Serpents." . . . 



" The movements of the Saurian reptiles are 

 effected principally by means of their feet, and in 

 some of the higher forms exclusively so ; but as 

 they descend towards the more elongated form of 

 the Skinks and other genera, in which these organs 

 become more and more subordinate, they are great- 

 ly assisted by the lateral motion of their bodies, 

 different parts of which are brought into alternate 

 contact with, and pressure upon either the rough- 

 ness of the ground or the shrubs and herbage 



