An easy walk from Lourdes through Lésignan, Paréac, Orincles, Leyrisse, and Bénac, to the return station of Ossun, traverses the entire outcrop of the Upper Cretaceous Flysch, lying between the abrupt uprise of the Cenomanien limestone at Lourdes and the Danien that skirts the Tertiary plain towards Tarbes. The age of this Flysch is admitted; every objection regarding it has been successively abandoned; and its appearance, composition, and characteristic fucoids are as typical at Lourdes as at any point within fifty miles on either side. By insensible gradations it passes repeatedly from fresh marly shale with characteristic fucoids into micaceous schists that have been classed as Cambrian. Portions of a sandy character acquire vivid colouring and pass insensibly into a rock indistinguishable from decomposed granulite, while preserving their original bedding. Such changes occur on either side, or on the prolongation, of extensive lenticular intrusions of solid granite, which cross the indicated route between Paréac and Orincles and between Orincles, Visker, and Bénac.