Middle and Upper Jurassic faunas have a wide distribution in the Canadian Arctic. The following index ammonites indicate the presence of various stages: Leioceras opa/inum, Pseudolioceras m'c/intocki (see Frebold, 1960) , and Erycites cf. E. howelli (lower Bajocian) ; Cranocephalites borealis and C. warreni n. sp. (probably upper Bajocian) ; Arkel/oceras tozeri, A. mc/earni, and Z etoceras thorsteinssoni n. sp. (probably upper Bajocian-lower Bathonian) ; Cranocephalites vulgaris (lower Bathonian); Arctocepha/ites elegans and A. cf. A. ornatus (middle Bathonian), Arcticoceras kochi and A. ishmae (upper Bathonian); Cadoceras spp. (upper Bathonian-lower Callovian) ; Cardioceras ex aff. C. mi rum (lower Oxfordian) ; Amoeboceras (upper Oxfordian-lower Kimmeridgian); Dorsoplanites spp. and Pavlovia? (?lower Volgian). No upper Volgian is indicated by ammonites, but Berriasian is present (Subcraspedites, Tallia, not described in this paper) .Some of the index ammonites have a restricted distribution in Arctic Canada as for example Erycites, Cranocephalites borealis, C. warreni and Arctocephalites that are known only from the Richardson and British Mountains region, and Arkelloceras, Cranocephalites vulgaris, Cardioceras and others, that seem to be restricted to some of the islands. Some of these differences may be explained by incomplete collecting, but others may be due to gaps in the sequences. There are close relationships with other Arctic faunas, particularly with East Greenland and the Chatanga region in northern Siberia. The manifestation of the boreal fauna realm took p lace in the Bajocian; the main connections of the boreal sea, which were closed at various times, were through the Scandic, the north Russian seaway and the north Siberian seaway.