Page:Popular Science Monthly Volume 68.djvu/531

Rh

 14. L.  of which there are about 150 known species between the borders of the United States and Patagonia.

the valley of the City of Mexico and the Lerma basin draining to the west, and the Rio San Juan, a tributary of the Panuco, draining to the east. While containing intrusive elements from the north, it contains none from the south, and its fauna is so distinct from either that there is slight hesitation in considering it as equivalent to the American, South American and Patagonian faunas.

The third, the South American fauna, is sharply divisible into the Brazilian and Andean. The Brazilian occupies the rivers from Southern Mexico to Buenos Aires and from Para to Callao, exclusive of the high Andes. This fauna is the richest in species in the world. From this region about ten per cent, of all the known fishes have been recorded. The Andean, from 3,000 to 5,000 feet and over above sea level, while possessing some forms in common with the Brazilian, is quite distinct. The species inhabiting this region would cause surprise if found at ManaosManaus [sic]; those of the Pacific slope would not.

The Patagonian fauna is among the poorest in the world. It occupies the Rio Negro basin, and everything lying south of it and a line joining it with Valparaiso. Its fauna has been considered in detail.

For convenience these faunal areas may be enumerated as the following 'regions' of unequal value. (1) Transition. (2) Mexican. (3) Brazilian. (4) Andean. (5) Patagonian. I am not sure but that the Titicacan basin constitutes a 'region' distinct from the Andean north of Titicaca.