40 THE WANDERINGS OF ANIMALS [CH. 



closed by neat valves. Some have strong ridges over 

 the eye-brow region, formed by modified scales to 

 make the sand fall off properly when the creatures 

 emerge. The ear-opening is protected by a fringe 

 of scales, or it is very small, even quite abolished. 



Most wonderful is the protection of the eyes. In 

 many desert lizards the lower eyelid has a trans- 

 parent disk in its middle, so that when this lid is 

 drawn up, the eye is closed and yet the lizard can 

 see. Several species of the Lizard genus Eremias in 

 India and Africa and the Indian Cdbrita possess such 

 a transparent window. In another Lacertid genus, 

 Ophiops, this arrangement is carried to the extreme. 

 The transparent lower lid is permanently drawn up 

 and fused with the rim of the much reduced upper 

 lid. Exactly the same modification has been hit 

 upon by Ablepharus, a genus of skinks widely dis- 

 tributed in the Old World, and by Xantmia in the 

 Californian and Mexican deserts. 



To enable certain lizards to run over the sand, 

 they have lateral fringes on the fingers and toes ; for 

 instance the North American Iguanid Uma, in Turkes- 

 tan and Persia the Agamid Phrynocephalus ; and what 

 is more surprising, the same occurs in some desert 

 geckos, e.g. Ptenopus and Stenodactylus of Africa, 

 and TeratoscincKs in Turkestan. Reference has been 

 made to the growth of the vegetation in patches. Con- 

 nected with this is the astonishing quickness of many 



