A Late Miocene Channel Catfish (Siluriformes, Ictaluridae, Ictalurus) from the St. Marys Formation, Calvert Cliffs, Maryland, USA John G. Lundberg and Kyle R. Luckenbill. Notula Naturae, No.485, May 2,2012, 32 pages. ABSTRACT.—Fossil remains of a catfish from the Late Miocene St. Marys Formation, Maryland, are described as a new, extinct species of Ictalurus (Ictaluridae). The holotype of †Ictalurus countermani n. sp., is a three-dimensional partial skull, Weberian complex, pectoral girdle and fin spine. Referred paratype specimens include isolated mesethmoid, premaxilla, dorsal-fin spine and cleithrum. †Ictalurus countermani n. sp., is distinguished among congeneric species by a combination of features of the sphenotic, cleithrum and pectoral-fin spine. The new species extends the known native geographic range of Ictalurus onto the mid-Atlantic slope and indicates extirpation of the genus from that region before the recent transplantation of the channel (I. punctatus) and blue (I. furcatus) catfishes. Fossils of gar (Lepisosteus) and bowfin (Amia) associated with †I. countermani corroborate the likely freshwater environment at or near the site of their burial. An additional catfish fin spine collected with the foregoing is identified as an ariid sea catfish, cf. Ariopsis felis.