Archaeocyatha from the Lower Cambrian of Wolf Lake and Quiet Lake areas in the Yukon Territory are described and illustrated. The fossils occur in carbonate rocks and are well preserved. Much of the necessary structural detail of the fossils is clearly observed in thin-sections and on polished surfaces of the specimens. The collection contains twenty-three species, twelve of which are new species. The new species described are: Ajacicyathus yukonensis, Coscinocyathus multiporus. Coseinocyathus cassiariensis, Coscinocyathus inequivallug, Coscinocyathus serratus, Coscinocyathus veronicus, Coscinocyathus tubicornus, Carinacyathus perforatus, Pyenoidocyathus solidus, Loculicyathus elliptieus, Metacoscinus poolensis, and Claruscyathus ketzaensis. The genera Carinacyathus and Loculicyathus are reported for the first time in North America. The Yukon fauna is dominated by Coscinocyathidae and Pycnoidocyathidae, showing close relationship to faunae in the Cordilleran region of British Columbia. It also shows relationship to Siberian and Australian faunae. This fauna is very different from the archaeocyathid assemblages in Nevada and California, where the dominant forms are Ethmophyllidae and Ajacicyathiclae. Arehaeocyatha have been instrumental in determining the age of rocks underlying a large area of the Yukon Territory. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate