Agalinis auriculata (Michx.) Blake (Scrophulariaceae) occurs in the Gravois Creek floodplain in southeastern St. Louis County, Missouri. This is the only known extant population of the taxon in Missouri. The threatened population of Agalinis auriculata is a relict at the periphery of the species range and suggests that wet meadows or mesic prairie once interspersed present-day bottomland forest at the site.