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78 the Patagoniano and, like the latter, to dip with a southward component. After an obscure space one comes to beds presumably lower, from the nature of the dip, consisting of silicified tuffs in part variegated + concretionary. Although not exactly similar to those of Coli-Huapi, with more white beds; these are probably the argiles fissilaires. Somewhat farther north comes the crest of what is apparently a very broad anticline + here beneath the arg. fis.-like series there is an upper thick series chiefly x-bedded sands + gravels and a lower series of tuffs similar to those of the Tertiary. We examined all these carefully and found no scrap of bone or tooth. Continuing north come successively higher beds until one finds small exposures of Tertiary tuffs definitely resting on argiles fissilaires. Here we found scraps of bone and fragments of mammal teeth, but nothing identifiable. The exposures are small + poor and they contain very few fossils and would not repay intensive work from the paleontological point of view. Near the Ensanche appears a lava flow, its relationships not clear from our hasty survey but apparently either on or in the Tertiary, +this eventually dips down northward into the valley, beyond which point there are no good exposures at least to the settlement. On the other side one also sees a thick somewhat folded + dislocated series of argiles fissilaires and resting on it some white beds. The latter were seen only from a distance as the exposure is too small to be of 79 much use and apparently identical with the almost barren beds seen directly across the river, + would have required one or two days more to visit and inspect. The road through the Sierra to Sarmiento has been studied by Feruglio, who has published a profile. The rocks are all Chubutiano. WORKING CAMP #2 Dec. 7, 1930-Dec. 15, 1930. About 10 leagues due north of Sarmiento,just east of the road from Sarmiento to the Laguna de los Palacios. A large shallow embayment against the lava-capped meseta of the Cerro del Humo and directly east across the valley from the Sierra de Castillo. Here a high barranca forms a large curve and the space in front of it is full of broken country, small mesetas, etc., with other Tertiary exposures. Locality indicated to us by Feruglio, who mentions it in his work. Ameghino's maps show a locality immediately north of the western end of Coli-Huapi, with Notostylopense and Pyrotheriense, and another northwest of this with Notostylopense and Astraponotense.