Strata of the Detroit River Group of north-central Ohio reflect restricted conditions of sedimentation during early Eifelian (early Middle Devonian) time that were transgressively displaced by normal-marine environments represented by the Columbus Limestone, which ranges from the middle costatus costatus Zone into the australis Zone and is capped by a disconformity interpreted as a wave-eroded surface. The overlying Delaware Limestone is assigned with uncertainty to the kockelianus Zone and reflects renewed transgression followed by a regressive phase. New taxa introduced include Icriodus stephensoni n. sp. and Polygnathus linguiformis alingulatus n. subsp. Several other forms that are either new or of uncertain taxonomic position are left in open nomenclature.--Modified journal abstract.