560 LACERTAE CHAP. 



The temporal region is covered over, as in the Lacertidae, 

 with strongly developed, bony, dermal ossifications. Similar 

 osteoderms underlie the scales which cover the body and tail. 

 The tongue is relatively short, not forked behind, and but very 

 feebly nicked at the tip ; it is covered with scale-like papillae. 

 Femoral pores are absent. 



All the Skinks prefer dry, sandy ground, in which they not 

 only burrow, but move quickly about, either for protection or in 

 search of their animal food. In connexion with this sand- 

 loving and at least temporary subterranean life stands the 

 frequent reduction of the limbs. Every stage from the fully 

 developed and functional pentadactyle limb to complete absence 

 of limbs is represented. There are species within the same 

 genus with five, four, three, or two fingers or toes. There are 

 Skinks without fore-limbs, but with vestigial hind-limbs, and 

 vice versa. The interesting point is that these reductions do 

 not indicate relationship within the family, but have happened 

 independently. They are impressive illustrations of convergent 

 retrogressive evolution. 



Ablepharus, widely distributed in the Old World, has the 

 lower eyelid transformed into a transparent cover, which is fused 

 with the rim of the reduced upper lid, exactly as in the Lacertine 

 genus Opkiops. 



All the Scincidae seem to be viviparous, some of them, e.g. 

 Tracliysaurus, in the strict sense of the word, since the hard or 

 parchment -like egg-shell has been dispensed with. 



The family contains about four hundred species, which have 

 been arranged in nearly thirty genera, many of them on fanciful 

 grounds. The family is cosmopolitan, but reaches its greatest 

 diversity in numbers and forms in the tropical parts of the Old 

 World, especially in the Australian region, inclusive of the 

 islands of the Pacific. America, notably South America, has 

 the smallest number. 



Trachysaurus, with one species, T. rugosus, inhabits the whole 

 of the Australian continent. It is easily recognised by the large 

 and rough scales, and the short and broad stump-like tail. It 

 is dark brown above with yellowish irregular markings ; the 

 under parts are yellowish, marked with brown. Embryos of 

 this species have yellow transverse bands on the back, but these 

 often fade away before birth. The creature is strictly vivi- 



