﻿Eigenmann : Magdalena Basin 



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Several genera pertain to the Andes and may be autochtho- 

 nous or may have come from the south. Astroblepus is a high 

 Andean genus forming the family Astroblepidse found in Vene- 

 zuela, Colombia, Ecuador, and Peru, possibly also parts of 

 Bolivia. Several species are found in the Magdalena basin. The 

 genera Lasiancistrus, Pseudancistrus, and Chsetostomus of the 

 Loricariidse or mailed catfishes have nearly the same distribution 

 as Astroblepus but do not reach such great altitudes. One species 

 of each genus is found in the Magdalena basin. The genus 

 Pygidmm is a swift-water mountain genus distributed from 

 southern Panama to Guiana and south to Rio Grande do Sul and 

 Patagonia wherever high altitudes or swift water form a suitable 

 environment for it. Several species are found in different parts 

 of the Andes within the Magdalena basin. 



Fifty-odd genera in the Magdalena basin, 76 per cent, are also 

 , found east of the easternmost Cordilleras. 



The rest are either peculiar to the Magdalena basin or to 

 the Magdalena- Atrato-Chagres-San Juan. These are in detail: 



Xyliphius confined to the upper Magdalena is an offshoot of 

 Bunocephalus, a genus widely distributed from the Atrato to 

 Paraguay but not yet caught in the Magdalena. Cetopsor- 

 hamdia and Nannorhamdia are catfishes derived from Pimelodella 

 — like Pimelodinse, which are found abundantly in our area as 

 well as east of the Andes. 



Eremophilus, confined to the plain of Bogota, is an offshoot 

 from Pygidium. It is a Pygidium without ventrals. 



Grundulus, also confined to the plain of Bogota, is a member 

 of the Cheirodontinse abundantly distributed in western Colombia 

 as well as all thru the east. 



Genycharax of the Cauca is either a derivative of Charax or 

 of Astyanax, both of which have a universal distribution in tropical 

 America. 



Microgenes and Argopleura are derivatives of Bryconamericus, 

 the latter found also in the Atrato and San Juan. 



Acestrocephalus replaces Acestrorhamphus of the east. Cteno- 

 lucinus replaces Xyphostomus. 



Gilbertolus is an offshoot from Charax. 



Othonophanes is derived from Brycon if distinct. 



There are no genera in all of these peculiar to the Magdalena 

 which might not equally well have developed anywhere east of 

 the Andes. Genycharax and Gilbertolus offer the greatest diffi- 

 culty. While some of them are highly interesting, even thrilling 



