This is the third of three volumes of Keys to the Trematoda, a series on the systematics and identification of the Class Trematoda. It covers five superfamilies with the Order Plagiorchiida and the family Didymozoidae, with the keys for their identification at the family, subfamily and generic levels. It also includes a key to all dignean superfamilies, including those treated in detail in volumes one and two.

Table of Contents:
1: Introduction and Key to Superfamilies 2: Superfamily Opisthorchioidea Looss, 1899 3: Family Opisthorchiidae Looss, 1899 4: Family Cryptogonimidae Ward, 1917 5: Family Heterophyidae Leiper, 1909 6: Superfamily Monorchioidea Odhner, 1911 7: Family Monorchiidae Odhner, 1911 8: Family Lissorchiidae Magath, 1917 9: Superfamily Gorgoderoidea Looss, 1899 10: Family Gorgoderidae Looss, 1899 11: Family Anchitrematidae Mehra, 1935 12: Family Brachycoeliidae Looss, 1899 13: Family Braunotrematidae Yamaguti, 1958 14: Family Collyriclidae Ward, 1917 15: Family Cortrematidae Yamaguti, 1958 16: Family Dicrocoeliidae Looss, 1899 17: Family Mesocoeliidae Dollfus, 1929 18: Family Orchipedidae Skrjabin, 1913 19: Family Paragonimidae Dollfus, 1939 20: Family Prouterinidae Foreyt, Schell & Beyer, 1996 21: Family Troglotrematidae Odhner, 1914 22: Superfamily Plagiorchioidea Lühe, 1901 23: Family Plagiorchiidae Luhe, 1901 24: Family Auridistomidae Stunkard, 1924 25: Family Cephalogonimidae Looss, 1899 26: Family Choanocotylidae Jue Sue & Platt, 1998 27: Family Dolichoperoididae Johnston & Angel, 1940 28: Family Echinoporidae Krasnolobova & Timofeeva, 1965 29: Family Encyclometridae Mehra, 1931 30: Family Gekkonotrematidae Yamaguti, 1971 31: Family Glypthelminthidae Cheng, 1959 32: Family Haematoloechidae Freitas & Lent, 1939 33: Family Leptophallidae Dayal, 1938 34: Family Macroderoididae McMullen, 1937 35: Family Meristocotylidae Fischthal & Kuntz, 1964 36: Family Mesotretidae Poche, 1926 37: Family Ocadiatrematidae Fischthal & Kuntz, 1981 38: Family Omphalometridae Looss, 1899 39: Family Opisthogonimidae Travassos, 1928 40: Family Orientocreadiidae Yamaguti, 1958 41: Family Reniferidae Pratt, 1902 42: Family Styphlotrematidae Baer, 1924 43: Family Telorchiidae Looss, 1899 44: Family Thrinascotrematidae Jue Sue & Platt, 1999 45: Family Urotrematidae Poche, 1926 46: Superfamily Microphalloidea Ward, 1901 47: Family Microphallidae Ward, 1901 48: Family Anenterotrematidae Yamaguti, 1958 49: Family Diplangidae Yamaguti, 1971 50: Family Eumegacetidae Travassos, 1922 51: Family Exotidendriidae Mehra, 1935 52: Family Faustulidae Poche, 1926 53: Family Gyrabascidae Macy, 1935 54: Family Lecithodendriidae Luhe, 1901 55: Family Leyogonimidae Dollfus, 1951 56: Family Pachypsolidae Yamaguti, 1958 57: Family Phaneropsolidae Mehra, 1935 58: Family Pleurogenidae Looss, 1899 59: Family Prosthogonimidae Luhe, 1909 60: Family Renicolidae Dollfus, 1939 61: Family Renschetrematidae Yamaguti, 1971 62: Family Stomylotrematidae Poche, 1926 63: Family Taiwantrematidae Fischthal & Kuntz, 1981 64: Family Zoogonidae Odhner, 1902 65: Family Didymozoidae Monticelli, 1888 66: Genera incertae sedis, genera inquirenda, nomina nuda, larval or collective names and recently erected genera