The only Lower Ordovocian trilobites known to occur in Ontario are a small collection of generally poorly preserved asaphid, bathyurid, and pliomerid trilobites from the Oxford Formation in the area between Ottawa and Brockville. This fauna consists of Bolbocephalus convexus (Billings), Gignopeltis rarus (Billings), Goniotelina subrectus (Bradley), Strotactinus salteri (Billings), and Isoteloides sp. This fauna is late Canadian and early Arenigian in age. The trilobite, conodont, and mollusk faunas indicate correlations of the Oxford Formation with the Phillipsburg 'Series' of Quebec, Fort Cassin Formation of New York and Vermont, mid- to upper St. George Group of Newfoundland, and mid-Fillmore Formation of Utah. A neotype is chosen for Strotactinus salteri.