Knowledge to date on the morphology of Fimbriaria tapeworms is summarised, with features of the genus being verified and augmented by some not previously taken account of, like the ultrastructure of the tegument. The most important features in accurate identification to the level of the species are the structure of the oncospheral envelope and the manner in which eggs are released from the uterus. Other features of diagnostic importance are the number of primordia of reproductive organs, the number of hooks at the cirrus base and the dimensions of the cirrus and cirrus pouches. A key to the identification of species is provided.