222 DR. H. GADOW ON MEXICAN [Juiie 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 ISTorthern 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 pai-t of Tepic ; there is also 

 little doubt that the peninsula of Lower California was continued 

 to the Revilla 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. 



Ophidia. 



Typhlopid.^. — Only two species are known from Mexico. 

 Typlilops tenuis from the State of Vera, Cruz, ranging south to 

 Guatemala; and Anomcdepis mexicana from Nuevo Leon. The 

 present centre of this family is South and Central America, 

 whence they have extended into the Antilles (Puerto Rico). 



Glauooniidji:. — 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 veiy scattered. The northern species, e. g. G. humilis, ranges 

 over the plateau and the Pacific slope ; G. clidcis from New 

 Mexico to Chilpancingo ; while G. alhifrons is a Centi-al American, 

 entering the Eastern and Western States of Mexico but avoiding 

 the plateau. 



BoiD^. — In Mexico only the Pythonine Loxoceinus hicolor, 

 I'ecorded from Colima, Tehuantepec, and Guatemala ; and the Boa 

 ■wiperator (inch mexicaiia), " Masacoatl," which ranges from 

 Ecuador through Central America into the Mexican Pacific and 

 Atlantic Tierra Caliente, keeping strictly to tlie 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, Corallus, and Ungalia, have allied 

 species in Central and South America. 



Consequently this archaic family is clearly divided into a 



