4 ON THE ZOOLOGICAL POSITION OF TEXAS. 



America proper, there are the two regions called respectively the 

 Austroripariau and the Sonoran, which are, climatically considered, of 

 the most diverse character.* The Austroriparian region is humid, 

 abounding in streams, and is covered with forests. Many species of 

 Batrachia are found within its limits, some of which rei)resent families 

 unknown to any other region of the earth. Water-tortoises and snakes 

 are numerous in species and genera, while the lizards have but few 

 representatives. The Sonoran region, embracing the elevated countries 

 of New Mexico and Arizona, is dry, with little vegetation, and a small 

 number of springs and rivers. Batrachia and water-tortoises are few in 

 species and individuals, while lizards and snakes are numerous in both. 

 This region, if characterized by its climatic and surface characters, has 

 considerable extent. It commences south of the center of Oregon, and, ex- 

 tending southward, embraces Nevada and Utah. Passing the Mexican 

 boundary we find the sage-brush-desert plateau east of the Sierra Madre, 

 the continuation of the Sierra Nevada, covering the greater i)art of Chi- 

 huahua, Coahuila, and Durango, and extending apparently as far to the 

 southward as Guanajuato, or more than half of the entire extent in lati- 

 tude of the Mexican Eepublic. At this point are found its character- 

 istic desert Batrachia, Biifo punctatus B. & G., B. dehilis Gird., and Spea 

 hammondi Bd. On the west coast, genera and species of the same region 

 have been found as far south as Mazatlan, such as Bufo dehilis, Sauro- 

 malus ater, TJta Mcarinata, &c. 



On the eastern coast no trace of the Sonoran Fauna has been found. 

 The low country, as already remarked, belongs to the northern extension 

 of the neotropical realm. This is separated from the barren plateau of 

 Coahuila and Durango by a mountainous region whose intermediate 

 elevation gives it the character from which it derives its name, the 

 Tierra Templada. Its width, at first small, increases southward, where 

 it expands so as to include, in all ];)robability, the beautiful valley of 

 Mexico. No corresponding belt of identical faunal character can be 

 determined on the western side of the plateau, since in Mexico as in the 

 continents which she connects, the Cordillera approaches iiear to the 

 Pacific, and the descent to the coast is rapid and abrupt. The Tierra 

 Templada is a garden region. Elevated above the hot lowlands of the 

 coast, the clouds from the Gulf discharge their burthen of rain on its 

 mountains and valleys, giving life and support to a varied vegetation. 

 The reptilian fauna of this region is in dh-ect contrast with that of the 



* See Check-List Batr. Reptil. N. America, 1875, p. 68, Bulletiu Natl. Museum No. I. 



