ABSTRACT: The Speed Member of the North Vernon Limestone (Eifelian, Middle Devonian) of southern Indiana contains three species of Polypora (Fenestellidae): P. laevinodata (Hall), P. adnata (Hall), and P. aculeata (Hall). Polypora laevinodata comprises 90 percent of the studied specimens. The polyporan fauna of the underlying Jeffersonville Limestone is stratigraphically and geographically closely related to the Speed polyporan fauna. Consequently, 13 species of Polypora described from the Jeffersonville Limestone by earlier authors have been studied and redescribed. Altogether, the 258 Speed and Jeffersonville specimens that were used in this study belong to seven species as described from an evaluation of 14 external characters. The species are: Polypora aculeata (Hall) [=P. submutans (Hall) = P. blandida Ulrich]; P. adnata (Hall); P. celsipora minima (Hall); P. laevinodata (Hall); P. quadrangularis (Hall) [=P. laevistriata (Hall) = P. straitopora (Hall)]; P. shumardii Prout [=P. cultellata (Hall)]; and P. transversa Ulrich. P. intermedia Prout is considered unrecognizable, as the types are lost and the species cannot be identified from the original description and illustrations. Faunal associations in the Speed Member indicate that it was deposited in an open marine environment. Phosphatic lag deposits suggest episodic nondeposition of carbonate. Functionally, the polyporans apparently were adapted to and thrived in unidirectional currents of modest velocity, probably 1 to 3 cm/sec.