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INDIANA UNIVERSITY STUDIES 



rier to the iutermingliDg of two fresh-water faunas. It is quite within 

 the range of possibilities that the Atlaiatic slope fauna ascended the 

 Chagres and suc-eeeded in crossing the low divide and descended the 

 Pacific rivers. The Chagres route has a rival farther south. In Colombia 

 the Cordilleras form four separate chains. The eastern, east of the Rio 

 Magdalena, the central, between the Magdaleua and its tributary, the 

 Cauca, the Avestern. west of the Cauca, and finally, a coast range. Be- 

 tween the western Cordillera and the coast Cordillera is a trough whose 

 highest point is but 300 feet above sea level. 



Tn the west Cordilleras to the east of this trough arise two rivers, 

 both of which flow into the longitudinal valley, where one, the Atrato, 

 flows to the north into the Carribean, the other, the San Juan, to the 

 south, and then through a break in the coast Cordilleras to the west to the 

 Pacific Ocean. The height of land separating the two systems scarcely 

 reaches a height of 100 m. This waterway is one of the strategic points 

 in the geographical distribution of South American fishes, and it is more 

 than to be regretted that there is not a single record of a fresh-water fish 

 fioni either of these rivers I 



'We are a little more fortunate about our knowledge of the fishes of 

 the two sides of Panama, but are far from an exhaustive knowledge on 

 the subject. 



'it would certainly be a disgrace not to make an exhaustive study 

 of the fresh-water faunas of the two slopes before there is a chance of 

 the artificial mingling of the two faunas. It ought to be urged upon 

 congress to make provision for the biological survey of the canal zone if 

 the president or the bureau of fisheries does not already possess authority 

 to provide for it. The work should be undertaken at once. 



•For the Inological survey of the Atrato-San Juan route we must de- 

 pend upon private enterprise, and it is to be hoped that the means for so 

 interesting and profitable work will not be lacking when the volunteers 

 for the work are so numerous and willing.' 



A partial examination of the material collected shows that for 

 several species of fishes tlie watershed between tl\e Atrato and San 

 Jnan is not a barrier. Even snch large species as Ctenohicius heani 

 Fowler are fonnd in both the San Juan and the Atrato Rivers. It 

 seems, however, that the ^channel' fishes of the Atrato have not 

 sncceeded in crossing to the San Jnan. They are not fonnd on the 

 Pacific slope. The details of the distribution will be given in the 

 final report which will be adequately. illustrated. 



