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PROCEEDINGS OF THE NATIONAL MUSEUM 



same extent as the Guanipa and Tonoro Rivers, the vegetation of 

 their flood plain is markedly more luxuriant. The profuse vegetation 

 of these two narrow strips of land is apparently at least partially due 

 to the fact that, in draining from the mountains to the north, the 

 Amana and the Guarapiche pass over exposed limestone strata, while 

 the Guanipa and Tonoro drain only the siliceous soil of the Mesa and 

 the relatively poor soil of the Sacacual-Las Piedras formation. 



BOLIVAR 



GEOLOGICAL FORMATION 

 ^^^ SACACUAL -LAS PIEDRAS 

 ^^H MESA 



Figure 46. — Sketch map of northeastern Venezuela, including area where birds were 



collected for this study. 



