1905.] AMPHIBIANS AND REPTILES. 221 



Igumiidm : 



1. Xerophile, humivagous ; Sonoran, non-Antillean. 



2. Arboreal ; Central and South American and Antillean. 

 Tejidce. — Neotropical, with Ameiva into Tierra Caliente and 



Antilles, Cneonidoj^horus far into United States. 

 Anguidce. — Mexican, Central American and Antillean, reaching 



far North and South. 

 Jienosauridce. 



XT 1 J .-i r Mexican, non-Antillean. 



tieiodertnatidce. 



Scincidce : 



1. Northern America and plateau of Mexico, non-Antillean. 



2, Central American into Mexico and Antilles. 

 Xantusiidce : 



1. Sonoran, non-Antillean. 



2. Central American and Antillean. 



Amphishcenidce. — Mexico, Central America, and Antilles ; 

 formerly much farther north in the United States ; extending 

 far into South America. 



These statements are intended, in their reduced form, to 

 indicate the probable centres of dispersal of the various families. 

 It is important that of these 10 families no less than 7 have 

 representatives in the Greater Antilles, and that these Insular 

 members belong, in not a few cases, to Insular, peculiar genera, 

 e. g. Cyclura and Metopoceros of the Iguanidse, Celestus of the 

 Anguidfe, Cricosatira s. Cricolepis of the Xantusiidfe ; and it is also 

 worth noting that Amjihishcena itself occurs in Puerto Rico, on 

 the Virginia Islands, and South and Central America, but not in 

 Mexico. Xenosaurus and Heloderma, each the sole member of a 

 family, are restricted to Mexico in a slightly wider sense. Most 

 of the Anguidaj and Iguanidte, and all the Xantusiidse, are centred 

 in tropical and semitropical America. We may fairly conclude 

 that at least the Amphisbfenidse, Anguidfe, Iguanidee, Xantusiidte, 

 are very old inhabitants of the ancient Sonoran-Central American 

 and Antillean mass of land. Of these families the Amphisbsenidse 

 may well be autochthonous. The Tejidas alone are unmistakable 

 Southern immigrants from an original centre, probably Brazilian, 

 not N.W. South Amei'ica ; otherwise it would not be obviovis why 

 only so few Tejida3 have extended beyond the present South- 

 American continent. They [Anolis and Ameiva) were the latest 

 immigrants into the Central Land Complex just before the 

 Antillean separation, after which these genera and Cnemidop>horus 

 could continue their continental progress northwards. 



It is suggestive that so many of these families fall into a north- 

 western, typically Sonoran and Pacific, xerophile, and a southern, 

 more Atlantic group with predominant hygrophile characters; 

 the Antillean forms naturally siding with the latter. The 

 Mexican plateau, instead of connecting, rather severs these two, 

 mainly oecological groups, the connection passing round to the south 

 of the plateau. It must remain a moot question which of the 



