The bay forms a fairly regular curve, broken on the French seaboard only by the estuaries of the Loire, Garonne, Adour and..
On the north their most noteworthy offshoots are, in the centre, the plateau of Lannemezan from which rivers radiate fanwise to join the Adour and Garonne; and in the east the Corbire.
To the maritime ports mentIoned above must be added the river pcsrts of Bayonne (on the Adour), Bordeaux (on the Garonne), Nantes (on the Loire), Rouen (on the Seine).
The basin of the Garonne occupies south-western France with the exception of the tracts covered by the secondary basins of the Adour, the Aude, the Hrault, the Orb and other smaller rivers, and the lowlying plain of the Landes, which is watered by numerous coast rivers, notably by the Leyre.
The Garonne rises in the valley of Aran (Spanish Pyrenees), enters France near Bagnres-de-Luchon, has first a north-west course, then bends to the north-east, and soon resumes its first direction.