passing south of Valladolid, with Toro and
Zamora on its right bank; then from a point 3 m. E. of Paradella to
Barca d'Alva it flows south-west and forms the frontier between Spain
and Portugal for 65 m. It crosses Portugal in a westerly direction
through a narrow and tortuous bed, and enters the Atlantic 3 m. below
Oporto at Sao Joao da Foz. The length of the Douro, which is greater
than that of any other Iberian river except the Tagus and Guadiana, is
probably about 485 m.; but competent authorities differ widely in their
estimates, the extremes given being 420 and 507 m. In Spain the Douro
receives from the right the rivers Pisuerga, Valderaduey and Esla, and
from the left several small streams which drain the Sierra Guadarrama,
besides the more important rivers Adaja, Tormes and Yeltes; in Portugal
it receives the Agueda, Coa and Paiva from the left, and the Sabor, Tua
and Tamega from the right. The area drained by the Douro and its
tributaries is upwards of 37,500 sq. m., and includes the greater part
of the vast plateau of Old Castile, between the watersheds of the
Cantabrian Mountains, on the north, and the Guadarrama, Gredos, Gata and
Estrella ranges, on the south. The lower stream is beset with numerous
rapids, called _pontos_, and is subject to swift and violent
inundations. On this account navigation is attended with difficulties
and risks between its mouth and Barca d'Alva; but a railway, running for
the most part along the right bank, skirts the river during the greater
part of its course through Portugal. The mouth of the river is partly
blocked by a sandy bar; only ships of light draught can enter, while
those of greater burden are accommodated at the harbour of Leixoes, an
artificial basin constructed about 3 m. N. On its way through Portugal
the Douro traverses the Paiz do Vinho, one of the richest wine-producing
territories in the world; large quantities of wine are conveyed to
Oporto in sailing boats. The Douro yields an abundance of fish,
especially trout, shad and lampreys.

DOUROUCOULI, apparently the native name (perhaps derived from their
cries) of a small group of American monkeys ranging from Nicaragua to
Amazonia and eastern Peru, and forming the genus _Nyctipithecus_. In
addition to the absence of prehensile power in their tails,
douroucoulis, also known as night-apes, are distinguished by their large
eyes, the sockets of which occupy nearly the whole front of the upper
part of the skul