My observations at Gavarnie commenced with the detection of the great fault of the Cirque, sketched in Bull. Soc. Géol. of 1868, and are summarized in my “Pyrenean Geology,” pp. 169, Dulau & Co., completed to 1907. The Hippurite limestone having been classed and mapped as typically metamorphosed Cambrian, on the ground that my maps and descriptions are à priori inexact, I have recently been concerned with the rectification of the simultaneously asserted Triassic age of the gypseous marls, which I have found to be Tertiary and Cretaceous, from Biarritz to Cardona. Before 1868 the Hippurites of Gavarnie and Heas were already described as anomalous by Leymerie in his Manual and papers, and by Frossard in his “Guide du Géologue.” The only specifically determined specimen mentioned by Bresson is from “near the Hourquette d'Alans,” a point touching the never-questioned Cretaceous beyond the great fault, and situated at 600 metres above the anomalous sheet in question, as it is figured on Bresson's largest sections. The only fossil of his basal Ordovician I had long previously ascertained to be in a fallen fragment from a peak to the west, outside the rocks in dispute. His ‘fundamental section’ east of Gedre is a local accident due to a fault, and his section of the Cirque is wildly in contradiction to the real stratification, as well as his section of the Spanish slope of the pass of La Canao and the Hount Sainte. All these errors are corrected on his definitive map of the French Survey, and in the report of the meeting of the Société Géologique in the Pyrenees in 1906. At that meeting the theory founded by M. Carez on the contradiction of my description of Eaux Chaudes, of Bull. Soc. Géol. of 1893, was explicitly acknowledged to be baseless and untenable by that writer himself, as well as by all present.