﻿Eigenmann: Fishes of Panama 



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changed natural conditions. The first one of these is Vaillant's 

 "Contribution a PEtude Ichthyologique du Chagres" (Bull. Mus. 

 d'Hist. Naturelle. 1897, No. 6, pp. 220-223). 



The second by myself (Science, N.S. XXII, pp. 18-20, July 7, 

 1905), besides listing the fishes recorded from the two slopes 

 made a plea for a thoro study before the canal should be completed 

 and unite the two faunas. The known facts concerning the fishes 

 were very far from complete. I said in part: 



I have just finished a consideration of the geographical distribution of the 

 fresh-water fishes of tropical America and Patagonia as applied to the 

 Archhelenis-Archiplata theory of von Ihering. The details will appear in 

 one of the volumes of the Hatcher reports of Princeton University. 2 The 

 evidence there collected indicates that the Pacific slope fauna of tropical 

 America has been derived from the Atlantic slope fauna. It is quite within 

 the range of possibilities that the Atlantic slope fauna ascended the Chagres 

 and succeeded 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 Magdalena and its tributary, the Cauca, the western, 

 west of the Cauca, and finally, a coast range. Between the western Cordillera 

 and the coast Cordillera is a trough whose highest point is but 300 feet above 

 sea level. 



In 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 Caribbean, 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 from either of these rivers ! 



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- sub- 

 ject. 



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 biological survey of the Atrato-San Juan route we must depend 

 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. 3 



2 "The Fresh-Water Fishes of Patagonia and an Examination of the Archiplata- 

 Archhelenis Theory". Reports of the Princeton University Expeditions to Patagonia, 

 III, 1909, pp. 225-374. Plates XXX-XXXVII. Maps. 



3 This work was later done by myself and Mr. Charles Wilson. The results have ap- 

 peared in these Studies, No. 46. 



