Large flat forms, genital pore _in front_ of ventral sucker, the latter powerful. Vitellariæ of numerous follicles, united by branching vitellarian ducts, at the sides of the body meeting posteriorly and extending ventrally and dorsally. Cirrus and vagina without spines. No crown of strong spines around sucker. Testes much branched. Uterus not well developed. Excretory bladder much branched. Eggs large. Sub-family. *Fasciolinæ*, Odhner, 1910. Large or median forms, gut much branched. Body has a shoulder separating head from body. Receptaculum seminis absent. Ovary branched, ventral sucker in anterior part of body. Genus: _Fasciola_. Sub-family. *Fasciolopsinæ*, Odhner, 1910. Shoulder absent. Receptaculum seminis present. Ovary branched, gut takes a zig-zag course with kinks on it, ventral sucker in anterior part of body. Genus: _Fasciolopsis_. Family. *Opisthorchiidæ*, Braun, 1901, emend. auctor. Ovary in front of testes. Small to medium flukes, very transparent, tapering anteriorly. Vitellaria moderately developed not extending in front of sucker. Cirrus absent. Seminal vesicle a twisted tube free in parenchyma. Testes near hind end one behind the other, lobed or branched, but not dendritically. Excretory bladder *Y*-shaped, the two limbs short, the stem *S*-shaped passing between the testes. Receptaculum seminis well developed. Laurer’s canal present. Uterine coils transverse, numerous. Eggs small. Sub-family. *Opisthorchiinæ*, Looss, 1899, emend. auctor. _Opisthorchiidæ_ in which the excretory pore is terminal. Excretory bladder long, dorsal to testes. Uterine coils not overlapping gut forks. Genera: _Opisthorchis_, _Paropisthorchis_, _Clonorchis_, _Amphimerus_, etc. Sub-family. *Metorchiinæ*, Lühe, 1909. _Opisthorchiidæ_ in which the excretory pore is ventral. Excretory bladder short, ventral to testes. Uterine coils partly overlapping gut forks and extend anteriorly beyond the sucker. Vitellaria compressed on the sides of the body. Genus: _Metorchis_. Family. *Dicrocœliidæ*, Odhner, 1910. Ovary _behind_ testes. Testes behind the ventral sucker, between it and the ovary. Body thin and transparent. Cirrus sac encloses the pars prostatica and seminal vesicle. Skin smooth. Gut forks do not reach posterior end. Receptaculum seminis and Laurer’s canal present. Vitellaria, moderate, lateral in mid-body slightly overlapping the gut. Uterus with an ascending and descending branch and numerous transverse coils extending to hind end. Eggs dark brown, 25 µ to 60 µ. Excretory bladder tubular in posterior third or half of body. Parasitic in bile-ducts of mammals and birds. Genus: _Dicrocœlium_. Family. *Heterophyiidæ*, Odhner, 1914.