An abundant and well preserved trilobite fauna is described from Upper Cambrian calcareous mudstones of the McKay Group, near Cranbrook in southeastern British Columbia. The trilobites are mostly articulated, consisting of similar numbers of molts and carcasses. They are representative of a new deep water biofacies, the Wujiajiania Biofacies, and a new Wujiajiania sutherlandi Fauna of late Steptoean age. The trilobites were collected from a narrow interval (<20 m thick) of richly fossiliferous strata, in a thick sequence of unfossiliferous to sparsely fossiliferous strata of similar lithology. The fauna includes fourteen species, six of which are new: Aciculolenus palmeri, Burnetiella leechi, Hedinaspis canadensis, Labiostria westropi, Pterocephalia norfordi, and Wujiajiania sutherlandi.