XII GEOGRAPHICAL DISTRIBUTION 501 



tropical regions, and also in North and Central America, not ex- 

 tending, however, into South America. Ilahuia, with more than 

 sixty species, occurs in the Palaeotropical and the Neotropical 

 regions. Whether these and other widely-distributed genera are 

 all natural is another question. 



The Agamidae, Varanidae, Lacertidae, and the Chamaeleontes 

 are restricted to the Old World. The Agamidae and Varanidae 

 have the widest distribution, occurring in the whole of the Old 

 World with the notalile exception of Madagascar and New- 

 Zealand. The Lacertidae are Palaearctic and Palaeotropical, being 

 however absent in Madagascar, and, broadly speaking, not extend- 

 ing eastwards beyond Wallace's line. It is a most suggestive 

 fact that most of those families of Eeptiles, and even of other 

 Vertebrates which have a wide distribution and are apparently 

 debarred from transgressing Wallace's line, are also absent from 

 Madagascar. 



The Chameleons are essentially African, with their centre of 

 greatest aljundance and development in Madagascar, only one or 

 two species occurring in Socotra, Southern Arabia, and in Ceylon 

 and Southern India. If they existed, or could be shown to 

 have existed, on the various islands in the Indian Ocean, for 

 instance in Mauritius and the Seychelles, the Chameleons would 

 be an excellent illustration of the former existence of a direct 

 land-connexion between Southern India and Southern Africa. 



The Iguanidae are essentially American, with the remarkable 

 exceptions of Cha.larodon and Hoplurvs in Madagascar, and 

 BracJiylophus in the Fiji and Friendly Islands. This peculiar 

 distribution finds some analogies in that of Dendrobatinae (p. 

 272), certain Boinae (p. 601), and Centetes and Solcnodon among 

 Insectivora. An Iguana (/. e/vrojiaea) has, however, been described 

 from the Eocene of France and England. The supposed relation- 

 ship of the Iguanidae with the Agamidae makes the problem 

 only more puzzling, since Agamidae are absent in Madagascar. 

 If we have recourse to the Zonuridae, which are confined to Africa 

 and Madagascar, and are supposed to be intermediate between 

 Anguidae and Iguanidae, then we may have ultimately to con- 

 clude that the Malagasy Iguanoid genera and the American 

 Iguanidae are a case of convergent evolution. 



The Amphisbaenidae are distributed over America, including 

 the West Indies, Africa exclusive of Madagascar, and the 



