Schematic representation of the measurements taken of the hard parts of specimens of Cichlidogyrus and Onchobdella. Structures from top left to bottom right: anchor, ventral transverse bar, MCO, dorsal transverse bar, vagina and hook. Abbreviations: I–VII, hook length; a, total anchor length; Ap, length of accessory piece; b, blade length; c, shaft length; d, guard length, e, point length; h, auricle length; He, Heel length; l, vagina width; L, vagina length; Pe, penis length; W, maximum width of ventral transverse bar; w, maximum width of dorsal transverse bar; X, branch length of ventral transverse bar; x, total length of dorsal transverse bar; y, distance between auricles.