Approx.) and follows a semicircular direction north-west and north to the source of the Javary (or Yavary), to include the basins of the Purus and Jurua within Brazilian jurisdiction.
The rivers forming this system are the Maranon from Puerto Limon to Tabatinga on the Brazilian frontier (484 m.), the Japura, Putumayo, Javary, Napo, Tigre, Huallaga, Ucayali, Pachitea, Jurua, Purus, Acre, Curaray and Aguarico all navigable over parts of their courses for steamers of 4 to 8 f t.
The inclusion of the upper waters of the Brazilian rivers Jurua, Purus and Acre is pro forma only, as they are wholly under Brazilian jurisdiction.
Which may account, perhaps, for its rarity, if, indeed, it be really scarce in its native home, which is probably the eastern slopes and tablelands of the Bolivian and Peruvian foot-hills bordering on Brazil, inclusive of the headwaters of the Purus, Acre and Jurua rivers.
The Jurua is the next great southern affluent of the Amazon west of the Purus, sharing with this the bottom of the immense inland Amazon depression, and having all the characteristics of the Purus as regards curvature, sluggishness and general features of the low, half-flooded forest country it traverses.