Page:Popular Science Monthly Volume 68.djvu/534

530 Andes east of Guayaquil before the Andes reached their present height. The Pacific slope fauna is less different from the Amazon fauna than that of the coastwise streams of Minas, if the number of peculiar genera is used as a measure of difference. The origin of the fauna of the plateau of Mexico is a separate subject.

The points of strategic importance for ichthyic chorology in South America are, therefore: (a) western Colombia and Panama; (b) Guayaquil to the Amazon, across the Andes; (c) the tableland of Guiana, Archiguiana; (d) the Rio San Francisco, with the Ria Parahyba and the headwaters of the Tieté and Rio Grande, in Archamazona; and (e) the area between the Rio Negro and the La Plata. It is these regions which will yield the richest scientific harvest to any museum undertaking South American exploration.