O. nasicola Witenberg, 1923 (& 1926)

Type host. Water rail, Rallus aquaticus Linnaeus ( Gruiformes: Rallidae).

Type locality. Russian Federation; specific type locality unknown.

Additional hosts. Glossy ibis, Plegadis falcinellus Linnaeus (Pelicaniformes: Threskiornithidae); little ringed plover, Charadrius dubius curonicus Gmelin ( Charadriiformes: Charadriidae) (northern subspecies of Charadrius dubius Scopoli)—(Yamaguti 1958, 1971).

Additional locality. Japan; specific locality unknown—Yamaguti (1971).

Previously proposed synonym. Ophthalmophagus massinoi Witenberg, 1926 — Bashkirova (1950).

Remarks. Considered a possible synonym of O. singularis (Stossich, 1902) by Dubois (1959). Joyeux & Baer (1927) considered this to be a species of Spaniometra. No oral or ventral sucker described—Witenberg (1923, 1926).