Opalinidae (Sarcomastigophora) in North American Amphibia. Genus Opalina Purkinje & Valentin, 1835

During 1992, the cloaca of 83 specimens of North American Amphibia from Algonquin Park and Kingston, Ontario, Canada, and from El Paso Country, Texas, USA, comprising 14 species in seven families, were checked for opalinids, Opalina martinonae n. sp. was found in five of nine Rana sylvatica (Ranidae); O. obtrigonoidea Metcalf, 1923 in six of 11 Bufo americanus (Bufonidae) and two of nine Pseudacris crucifer (Hylidae); O. pickeringi Metcalf, 1923 in two of nine Pseudacris crucifer and in one of six Rana pipiens; and O. virguloidea Metcalf, 1923 in two of six Hyla versicolor (Hylidae). Opalina flava Stokes, 1844 is proposed for Cepedea flava (Stokes, 1884) Metcalf, 1923. The occurrence, evolution and biogeography of North America Opalina are discussed.