﻿Indiana University Studies 



In the "Upper Magdalena" are included all that are known 

 from south of La Dorado m the main stream and its larger tribu- 

 taries to (including) Ibague. It should take in the contents to 

 Neiva. In reality all we know has come from between Honda 

 and Girardot with the tributaries in this short stretch. Many or 

 all of these will also be found in the lower Magdalena. There is 

 always a reasonable expectation that the fishes in any stretch 

 will be found lower down and there is no sharp break between 

 Honda and the river below La Dorado. 



Similar y the column for the Cauca should include everything 

 from the rapids below Cartago to the head of navigation, but 

 nothing is known from Cali upward. 



Finally, the last column includes a variety of streams from the 

 highest altitudes clown to the mouths of the streams where tor- 

 rential conditions give place to large stream conditions. I give 

 the highest known altitude in feet where it was obtainable. In 

 some cases the altitude may be the sole factor determining the 

 presence or absence of a species. In many others torrential con- 

 ditions that frequently go with altitude determine the distribu- 

 tion. 



Of the species found in the upper Cauca, 11 are also found m 

 the upper Magdalena and 5 in the lower Magdalena. 



Of the 54 species in the upper Magdalena, 32 are also found in 

 the lower Magdalena. 



Conclusion. The above analysis demonstrates that the 

 fish fauna of the Magdalena basin was derived in small part from 

 the ocean and in larger part from Central America. It demon- 

 strates beyond a peradventure that most of it had an origin in 

 common with that of the Orinoco basin to the east of it, and that 

 the fauna of the Magdalena was segregated from the general fauna 

 of the Orinoco by the formation of the Cordillera of Bogota 

 between the two, at a time antedating the development of most 

 of the present species. It also demonstrates that if the above 

 conclusions are valid some species found on both sides antedate 

 the formation of the Cordillera of Bogota; that the stripes of the 

 large catfish, the Bagre tigre have persisted during the entire 

 time since the Cordillera of Bogota began to be an effective 

 barrier against the intermigration of the fishes of the two sides. 



