A sequence of Valanginian rocks was studied in the part of the depocentre of the Sverdrup Basin, now occupied by Amund Ringnes and Ellef Ringnes islands. The about 500 m thick Valanginian sequence is represented mostly by the upper part of the Deer Bay Formation. Bed by bed collecting of fossils resulted in an improvement of our knowledge of the succession of ammonite species in the report area. Only high-boreal to arctic species occur in the lower part of the particularly thick (about 300 m) lower Valanginian. The upward fauna] sequence is: Temnoptychites, Thorsteinssonoceras, Polyptychites (Siberiptychites n. subgenus) ex gr. stubendorffi. In the younger lower Valanginian these faunas are replaced by those consisting of true Polyptychites. The latter faunas originating in the more temperate regions of the Boreal Realm consist of P. keyserlingi fauna below and P. spheroidalis fauna at the top. These beds also contain new, very large Polyptychites species. The lower part of overlying lower upper Valanginian beds contains a new Prodichotomites species which is then replaced by repre sentatives of Homolsomites. No ammonites have been found in the topmost beds of Deer Bay Formation which only yielded a late Valanginian Buchia fauna.