Lower Jurassic and lower Bajocian faunas are widely distributed in the Canadian Arctic, particularly in the Arctic Archipelago, where marine lower Sinemurian, Toarcian, and Bajocian are represented. In the Aklavik Range (northeastern Richardson Mountains, Arctic Coast region) lower and upper Sinemurian rocks are present; farther to the west lower Sinemurian, upper Pliensbacbian, Toarcian and Bajocian are indicated. The index ammonites described in this paper are: lower Sinemurian-Arietites sensu lato gen. et sp. indet.; upper Sinemurian, zone of Oxynoticeras oxynotum- 0 . oxynotum (Quenstedt), Gleviceras ? sp. indet., Arctoasteroceras jeletzkyi n. gen., n. sp.; upper Sinemurian, probably zone of Echioceras raricostatum-Echioceras sensu lato sp. indet.; Pliensbachian- zone of Amaltheus margaritatus- Amaltheus sp.; Toarcian- Dactylioceras commune (Sowerby), Catacoeloceras spinatum (Frebold), Catacoeloceras po/are (Frebold), Harpoceras cf. exaratum (Young and Bird), Pseudolioceras aff. compactile (Simpson), Grammoceras ? sp. indet.; Bajocian- L eioceras opalinum (Reinecke), Pseudolioceras m'clintocki (Haughton), Pleydellia ? sp. indet., Erycites cf. howelli (White). Both in the Richardson Mountains and on the islands the sequence is very incomplete; the Hettangian and most of the Pliensbachian are apparently entirely absent, or, in the case of the Hettangian possibly represented by nonmarine deposits locally. Fauna! gaps occur in the Sinemurian and Toarcian. Compared with the northwest European standard section of the Lower Jurassic only six of the seventeen ammonite zones are found in the Canadian Arctic. Several transgressions and regressions took place in this area during the Early Jurassic and Bajocian. Close fauna! and stratigraphic relationships with the Barents shelf and East Greenland are established. Zoogeographically most of the ammonites belong or are related to species of world-wide distribution.