Two new genera of cheirurinid trilobites are described from the lower Whittaker Formation (?Rocklandian to Edenian; late Middle and early Late Ordovician) of the southern Mackenzie Mountains. The monotypic genus, Whittakerites n. gen., is a probable descendant of Ceraurus and is presently known only from northern Canada. Borealaspis n. gen. is established for two species from northern Canada, one of which possibly occurs in northern Greenland, and includes B. numitor (Billings) from Anticosti Island. New species described are Whittakerites planatus, Borealaspis whittakerensis, and B. biformis.

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