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Show 2 2 2 DR. H. GADOW ON MEXICAN [June 6, two groups is the older. Not unlikely both are, in America, the divergent result of more generalised features; the one with the desert, the other with the typical forest as the leading motive, or rather the ultimate theme or goal for adaptation. We do not know the physical features of ancient Sonoraland. There need have been no deserts or semiarid tracts and rather barren plateaus. The " petrified forest" of Arizona; the fact that many of the present desert-like stretches from Northern Mexico, through New Mexico to Utah and beyond, are the basins of former lakes (many of them still rapidly receding); nay, even the prehistoric towns in the now inhospitable parts of Arizona and New Mexico-all these circumstances indicate that much of Old Sonoraland is still further tending towards the formation of deserts, just as clearly as enormous parts of Central Asia. Sonoraland had originally a much wider extent. It is obvious that the Tres Marias Islands were part of Tepic; there is also little doubt that the peninsula of Lower California was continued to the Bevilla Gigedo Islands. That was at an epoch when the Gulf of California did not yet exist, the peninsula as such dating from the end of the Miocene. O p h id ia . T y p h l o p id .e .- Only two species are known from Mexico. Typhlops tenuis from the State of Vera Cruz, ranging south to Guatemala; and Anomalepis mexicana from Nuevo Leon. The present centre of this family is South and Central America, whence they have extended into the Antilles (Puerto Rico). G l a u c o n i id .e .-Glauconia, the main genus, ranges from New Mexico, Texas, and Florida, far into South America, whence only the Lesser Antilles have been entered. Mexican localities are still very scattered. The northern species, e. g. G. humilis, ranges over the plateau and the Pacific slope ; G. dulcis from New Mexico to Chilpancingo ; while G. cdbifrons is a Central American, entering the Eastern and Western States of Mexico but avoiding the plateau. B o i d . e .- In Mexico only the Pythonine Loxocemus bicolor, recorded from Colima, Tehuantepec, and Guatemala ; and the Boa imperator (incl. mexicana), " Masacoatl," which ranges from Ecuador through Central America into the Mexican Pacific and Atlantic Tierra Caliente, keeping strictly to the forest and bush lands. The Boinse continue northwards as the arenicolous Lichanura of Lower California and of similar hot desert-like districts of Arizona; and the likewise arenicolous Charina, which extends from California to Washington. Another set of Boas, typical dwellers of luxurious tropical countries, occurs in the Antilles; all these, Epicrates, Cor alius, and Ungalia, have allied species in Central and South America. Consequently this archaic family is clearly divided into a |