118 ANIMAL LIFE IN DESERTS 



complement of four legs to complete absence of 

 Mmbs. 



Many lizards living in sandy places are extremely 

 rapid in their movements. When they are not 

 running they stand alert with the head held high 

 and the front part of the body raised on the fore-legs, 

 and when they are in motion the tail is held weU 

 above the ground as a counter-balance. This holds 

 good of lizards of several families, from several parts 

 of the world ; and the species which are predaceous 

 and those which are preyed upon both exhibit it. 

 In many of them the toes of the fore- and hind-feet 

 are broadened by a fringe of elongate scales. Appar- 

 ently aU of these species Hve on sand, some of them 

 on great stretches of dune, others on the small heaps 

 of blown sand which accumulate under bushes in 

 deserts of mixed stone and earth : it seems legitimate 

 to conclude that the fringe widens the surface, which 

 presses on loose sand and acts in the same way that 

 a snow-shoe does on loose snow. As Figs. 39 and 40 

 show, these fringes are developed in several families 

 of lizards, in deserts in different parts of the world. 

 Of the seven genera figured Phrynocephalus (A) is 

 an Agamid from Transcaspia ; Acanthodactylus (B) 

 and Scaptira (C) are Lacertidse, distributed in the 

 Great Palsearctic Desert ; CaUisaurus (D) is an 

 American Iguanid ; Teratoscincus (E), Stenodactylus 

 (F), and Ceramodactylus (G) are Palsearctic desert- 

 Hving Geckonidse. It is clear that this curious 

 character has been developed on at least half a 

 dozen different occasions, and it is clear also that it 

 is a response to Ufe on sand. I am most grateful 



