GECKOS, LIZARDS, AND CHAMELEONS. 89 



These they enter head-first, and leave the tail to 

 block the entrance thereto. These lizards are 

 purely vegetable feeders, and have a wide distribu- 

 tion, occurring in North Africa, Arabia, Syria, 

 Persia, and North- Western India. 



There is nothing about the general appearance 

 of Uromastix, to which reference has just been 

 made, that would lead one to suppose that it was 

 a burrowing animal. The same is true of several 

 other lizards. Thus the members of another 

 genus Liolepis of this family, Agamidse, live 

 in holes in the ground, which may run vertically 

 downwards for as much as two feet before there 

 is a bend in their course. Each burrow is in- 

 habited by a pair of lizards. The same absence 

 of any peculiar modification is true of the remark- 

 able Conoloplms of the Galapagos Islands. This 

 is possibly due to the fact that burrowing is only 

 an incident in the life-history of these species ; 

 that is to say, existence does not depend on their 

 ability to burrow. With many other species, 

 however, it would appear to be otherwise. Thus 

 the eyes in many sand-burrowing lizards are pro 

 tected by a transparent disc of skin on the lower 

 eyelid, so that this can be drawn over the eye 

 and yet leave the sight unimpaired. In the 

 genus Ophiops, of North Africa and India, the 

 lower eyelid and its window-pane is permanently 

 fused with the upper lid so that the eye is shielded 

 as in the G-eckos, though it will be remembered 

 in this case the protection was afforded by a 

 different means. 



A considerable number of lizards, however, 

 belonging to widely different families have 



