East and south of the Sierra de Merida and the Maritime Andes the region is thinly populated and little known.
In most parts ofithe Peruvian Andes the line of perpetual snow is at 16,400 ft.; but on the Cordillera Nevada, above the Callejon de Huaylas, it sinks to 15,400 ft.
The Peruvian chinchilla (C, brevicaudata) is larger, with relatively shorter ears and tail; while still larger species constitute the genus Lagidium, ranging from the Andes to Patagonia, and distinguished by having four in place of five front-toes, more pointed ears, and a somewhat differently formed skull.
The central chain is connected with the Eastern Andes by the transverse mountain-knot of Vilcanota, the peak of that name being 17,651 ft.
Pedro de Valdivia in 1540 made an expedition into the country of the Araucanian Indians of Chile, and was the first to explore the eastern base of the Andes in what is now Argentine Patagonia.
Annually, but the drainage from the eastern slopes of the Andes is large enough to meet the loss from evaporation and keep these inland lakes from drying up. At an early period this depressed area drained southward to the Colorado, and the bed of the old outlet can still be traced.
The Chilian and Peruvian Andes and Patagonia are the homes of two peculiar deer locally known as guemals (huemals), and constituting the subgenus Xenelaphus, or Hippocamelus.
This definition unfortunately ignored the fact that the Andes do not run from north to south in one continuous line, but are separated into cordilleras with valleys between them, and covering in their total breadth a considerable extent of country.
Along the Brazilian frontier and about the sources of the Orinoco tributaries on the eastern slops of the Andes there are extensive forests, sometimes broken with grassy campos.
Coca, one of the most important plants of the country, is cultivated on the eastern slopes of the Andes at an altitude of 5000 to 6000 ft., where the temperature is uniform and frosts are unknown.