The reservoir reef carbonates at the Bent Horn field have been referred to as the Blue Fiord Formation, but they are younger than the type Blue Fiord of Ellesmere Island. The top of these carbonates, from which the stromatoporoid fauna is here described, is dated by conodonts as of Eifelian age. They are the same unit that has also been called the Unnamed Formation. Fourteen taxa of stromatoporoids, none of them described here as new, are identified from cores. Five species are common to the fauna of the Unnamed Formation of surface exposures on Bathurst and Truro islands. The ranges of the three species from the fauna of the typical Blue Fiord of Emsian age are extended into this Unnamed Formation. A synthesis of the paleontological evidence suggests that the top of the reservoir is basal Eifelian age. The recognition of Pseudoactinodictyon cf.P. stearni and Simplexodictyon vermiforme at Bent Horn suggests paleogeographic connections to the Great Lakes and Yukon stromatoporoid faunas of this age.