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BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



consideration of wbich it is not proposed at present to enter. These 

 are the Upper Amazonian Province, embracing the region drained by 

 the Upper Amazon and its principal tributaries (Western Brazil and 

 those portions of Peru and Bolivia east of the ^ndes) ; the Lower Ama- 

 zonian Province, embracing the Lower Amazonian and Orinoco Basins ; 

 and the Southeast Brazilian Province, embracing Southeastern Brazil 

 and Paraguay. They are characterized by the occurrence of numerous 

 peculiar species rather than by peculiar genera. The genus Lagotlirix 

 appears to be confined, however, to the Upper Amazonian Province, 

 Chrysotlirix to the Lower Amazonian, and Brachyteles to the Southeast 

 Brazilian, where occur also Icticyon, Thous, Lycolepex, etc., not found in 

 the other regions, but ranging thence southward to Patagonia. 



Genera of the Brazilian Region. 



