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Show 1905.] AMPHIBIANS AND REPTILES. 2 2 1 Iguanida): 1. Xerophile, humivagous; Sonoran, non-Antillean. 2. Arboreal; Central and South American and Antillean. Tejidce. Neotropical, with Ameiva into Tierra Caliente and Antilles, Cnemidophorus far into United States. Anguidce. Mexican, Central American and Antillean, reaching far North and South. Xenosauridce. 1 , T Heloder mat idee, j Mexican' ^on-Antillean. Scincida?: 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. A mphisbcenidce.-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 Iguanida?, Celestus of the Anguidse, Cricosaura s. Gricolepis of the Xantusiidte ; and it is also worth noting that Amphisbcena itself occurs in Puerto Rico, on the Yii'ginia 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 Anguidse and Iguanidae, and all the Xantusiidse, are centred in tropical and semitropical America. We may fairly conclude that at least the Amphisbaenidae, Anguidae, Iguanidae, Xantusiidae, are very old inhabitants of the ancient Sonoran-Central American and Antillean mass of land. Of these families the Amphisbaenidae may well be autochthonous. The Tejidae alone are unmistakable Southern immigrants from an original centre, probably Brazilian, not N.W. South America ; otherwise it would not be obvious why only so few Tejida? 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 ancl Cnemidophorus could continue their continental progress northwards. It is suggestive that so many of these families fall into a northwestern, 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 |