Nine new species of bryozoans belonging to the orders Cyclostomata and Trepostomata are described from exposures of the Amsden formation in Madison and Jefferson counties, southwestern Montana. Four species are assigned to the cyclostomatous genera Fistulipora, Cyclotrypa, and Dybowskiella, and five species to the trepostomatous genera Tabulipora and Stenophragmidium. The range of Stenophragmidium, which apparently has not been hitherto recognized in North America, is extended to include its occurrence in strata of probable Pennsylvanian age.

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