Six subsurface reef complexes in the Swan Hills area, rich in stromatoporoid and associated faunas, are easily correlated; nine separate stages of reef growth, from bottom to top, are designated Divisions I to IX of the Swan Hills Formation. Five of 31 recognized stromatoporoid species are new; dendroid forms are allied genetically to both subspherical and tabular forms. It is proposed that growth form be given little importance for taxonomic purposes. Progressive loss of species at end of each stage of reef growth is most significant between Divisions V and VI, where a break indicates a disconformity marking considerable lapse of time at the Middle-Late Devonian boundary. Diagnostic Middle Devonian ostracodes also disappear at this level, and no later Devonian was recovered above it. The enclosing Waterways Shale contains a Late Devonian microfauna.

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