1911.] NATURAL SCIENCES OF PHILADELPHIA. 493 



NEW FRESH-WATER FISHES FROM WESTERN ECUADOR. 

 BY HENRY W. FOWLER. 



A small collection of fishes, secured in the affluents of the Chimbo 

 River near Bucay, in the Province of Guayas, Ecuador, in July of 

 1911, was recently submitted to me for study by Mr. S. N. Rhoads. 

 At present this collection is placed on deposit in the Academy. 

 As the region in question presents some interesting hydrographic 

 features, Mr. Rhoads kindly contributes the following notes, gathered 

 from his recent explorations in the country where he obtained the 

 collection. 



"The Rio Chimbo, joining the Rio Chanchan several miles below 

 Bucay, flows almost directly southward from its source in the western 

 foothills of Mount Chimborazo for a distance of about 50 miles. It 

 is more practically isolated in a faunal sense from the sources of all 

 the other river systems of Ecuador flowing into the Pacific than any 

 other watercourse of its size in that country. This is due to its 

 being hemmed in both east and west by the lofty parallel ranges of the 

 Main or Central Cordilleras and that of the Pacific system of moun- 

 tains which goes by the name of the Western Cordilleras. Until 

 it joins the Chanchan, its waters have no alternative but to con- 

 tinue their precipitous and turbulent course due south as in a mighty 

 trough, but there, having reached more level and less elevated 

 country, its course naturally deflects almost at right angles and 

 makes a short cut for the ocean via the mighty Guayas. The 

 Chimbo is characteristic of all those rivers of western Ecuador 

 which owe their origin, as well as their perpetuity during the dry 

 season, to the snow- and glacier-fed springs of the great peaks of the 

 Andean system which rise to an elevation of 15,000 to 20,000 feet 

 above sea level. The greater part of the lofty country drained by 

 these rivers is extremely precipitous, almost denuded of forest growth 

 and trampled by cattle. The soil is filled with boulders and pebbles, 

 and the rock- and mud-encumbered river channels are continually 

 changing base with every sudden rise of the water. Couple this 

 with a continuous gradient of the river bed of 5 to 15 and even 20 

 per cent, and one begins to understand why only one species of fish 

 can exist in these waters at elevations of over 3,000 feet. Even 

 below this there are very few species to be found in the main channel 

 until the upper edge of the lowland terraces appears, at about 1,000 

 feet above the sea, and even here the majority of the fish fauna 

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