80 Mr, G. A. Boulenger on the Geographical 



regards groups of higher rank, and the changes from the centre 

 towards the North and South are very gradual. And it is note- 

 worthy that the Central- American fauna (of which the North- 

 American is but an offshoot) presents a greater variety of 

 types than South America ; thus it possesses representatives 

 of every one of the eleven families which occur in the realm, 

 viz. Geckonidse, Eublepharidse, Iguanidge, Xenosauridae, 

 Anguidse, Aniellidse, Helodermatidse, Xantusiidge, Teiidge, 

 Amphisbsp.nidge, and Scincidse; whereas South America lacks 

 the small groups Eublepharidse, Xenosauridae, Aniellidse, 

 Helodermatidse, and Xantusiidse. As the greater abundance 

 and variety of forms of the Anguidae occurs in the northern 

 half and the West Indies, and the reverse is the case as re- 

 gards the Teiidte (especially with reference to variety of 

 genera) and the Araphisbajnidae, we may safely draw the 

 boundary -line between two regions or subregions, as it may 

 be thought fit to term them, at the Isthmus of Panama, the 

 West Indies being comprised with the northern region. 

 Lizards range only as far north as British Columbia [Ger- 

 rJionotus ccerideus)^ Minnesota {Eumeces septentrionalis) ^ and 

 Massachusetts [Eumeces fasciatus) ; whilst they have pene- 

 trated to the Straits of Magellan [Liolcemus magellanicus) . 



In the following remarks on the Palceogean Realm Wallace's 

 zoo-geographical division is followed, with the view of exami- 

 ning how far it agrees with the facts deducible from the 

 distribution of the Lacertilia. 



1. The Palcearctic Region. — There is no more reason for 

 separating this region from Tropical Africa than there is for 

 separating North from Tropical America. Its chief character 

 is the abundance of Lacertidae, which group is also richly 

 represented, by identical or closely allied genera, throughout 

 the continent of Africa. In the Oriental Region they disap- 

 pear, being eastwards represented only by the aberrant genus 

 Tachydromus, which is an Oriental form. 



In Europe and the Mediterranean district Anguidaj occur, 

 represented by two genera, viz. Anguis, which has its nearest 

 ally in Ophiodes of South America, and Pseudopus (of which 

 a second species is found in the Khasia hills), closely related 

 to Ophiosaurus of North America. The occurrence of these 

 American types is analogous to that of the Batrachian genus 

 Hyla in the same region, and the fact that the Khasia hills 

 are also the home of a distinct species of that genus is ex- 

 tremely remarkable ; but this is the only analogy that can be 

 found between the Batrachian and Lacertilian faunas of the 

 Palaearctic Region, The Mediterranean districts of Africa and 

 Asia, as well as the tract extending to North-western India, 



