﻿ICHTHYOI-OGTCAI; RE(X)NNAISSANCE OF COLOMBIA. 



3 



Several years ago, the author of this paper pointed out that, 

 with a sin pie exception, the nearest relatives of the Pacifie slope 

 fauna are found in the valley of the Mag'dalena. This single ex- 

 ception has been removed hy the present expedition, for it was 

 found that the Cetopsinae are abundant in the upper Magdalena 

 and Cauca. No Amazonian genus that has found the eastern Cor- 

 dilleras of Colombia an impassable barrier is found in any of the 

 Pacifie slope streams from Pei'u to Mexico. This probably means 

 that no lowland 5shes have crossed the Cordilleras south of Co- 

 lombia. The importance of a survey of the fauna of the Magdalena 

 is apparent. 



The importance of the San Juan and the Atrato in the study 

 of the fauna of the Atlantic and I'acific slopes of South America is 

 self-evident to any one familiar with the physiographic features of 

 these rivers. They flow in opposite directions in the same trough ; 

 the watershed separating some of their headwaters is insignificant, 

 in elevation not much, if any, over 300 feet above sea level. The 

 Atrato is a large stream, of apparently easy access to the fauna of 

 the Magdalena, and the San Juan is the largest of the South Amer- 

 ican rivers flowing into the Pacific. 



The main problem I endeavored to solve in Colombia is: What 

 is the relation of the fauna of the San Juan to that of the Atrato: 

 and what is the relation of the fauna of the Atrato to that of the 

 Magdalena ? Supplementary problems considered are : What is the 

 nature of the fauna of the plains of Bogota; what is the relation, 

 of the fauna of the uppei' Cauca, above Cartago, to that of the 

 upper Magdalena ; what is the vertical distribution of the species 

 in the Pacific slope streams as illustrated by the Rio DagTia? 



As icnsr a go as the year 1891, the author planned an expedition 

 to Colombia.^ Twenty-one years later, during January, February, 



1 The following- letter, In answer to one of inquiry, was received about tliat 

 time : 



U. S. Legation. 



Bogota, Marcli 29, 1802. 



Pi'of. C. H. Eigenmann. 

 Dear Sir : 



I am in receipt of your valued favor of the 22d ult. and have carefully noted 

 its contents. 



So far as I know, there are only two specimens ov kinds of fish in this plain, 

 or nearer it than the Magdalena River, some 80 miles away — that river is quite 

 rich in fish, some of them very large. 



The fish of this plain are the 'capitan' and the 'guapucha' — of the former you 

 seem to know something. The latter is a little fellow not over two inches long — I 

 think I can get you some specimens. Pei*haps the better way would be to send 

 them home by my wife in August, who could mail them to you from New York. 

 You say in your letter that you send instructions on a separate sheet, but you 

 failed to do so. 



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