The surface features consist of an immense elevated plateau with a chain of mountains on its eastern and western margins, which extends from the United States frontier southward to the Isthmus of Tehuantepec; a fringe of lowlands (tierras calientes) between the plateau and coast on either side; a detached, roughly mountainous section in the south-east, which belongs to the Central American Plateau, and a low sandy plain covering the greater part of the Isthmus of Yucatan.
Descending to the lowlands on either side of the plateau, the temperature rises steadily until the upper limit of the tropical region, called tierras calientes, is reached, where the climate is hot, humid and unhealthy, as elsewhere in the forested coastal plains of tropical America.
The tierras calientes (hot lands) of Mexico include the two coastal zones, the Isthmus of Tehuantepec, the states of Tabasco, Campeche, and part of Chiapas, the peninsula of Yucatan and a part of eastern Oaxaca.
Another hot, dry climate is that of the tierras calientes of Sonora.
Bancroft (Resources of Mexico, pp. 3-4), the tierras calientes, which include a coastal zone 30 to 40 m.
The sanguinary vampire (Desmodus rufus) has an extensive range through the tierras calientes and tierras ternpladas of the southern states.
For convenience of description, the flora of Mexico may be divided into four great divisions: that of the comparatively barren plateau and the arid coast regions, the humid tierras calientes, the intermediate tierras templadas and tierras friar, and the higher regions of the sierras.
In the intermediate zones between the higher sierras and the tierras calientes the flora is very largely composed of species characteristic of the bordering hot and cold regions.
An important product of the plateau and of the open districts of the tierras calientes, growing in the most arid places, is the " nopal " or prickly pear cactus (Opuntia ficus indica).
In the tierras calientes of Mexico, however, better conditions prevail.
JALISCO, XALISCO, or Guadalajara, a Pacific coast state of Mexico, of very irregular shape, bounded, beginning on the N., by the territory of Tepic and the states of Durango, Zacatecas, Aguas Calientes, Guanajuato, Michoacan, and Colima.
It once formed part of the reyno of Nueva Galicia, which also included Aguas Calientes and Zacatecas.