S. japonicum (Kurisu, 1932) n. comb.

Type host. “ Domestic fowl”; species unknown—most likely the chicken, Gallus gallus domesticus (Linnaeus) ( Galliformes: Phasianidae)— Uchida (1991).

Type locality. Japan; specific type locality unknown.

Remarks. This species was originally described as Cyclocoelum japonicum Kurisu, 1932 . It was considered to be a synonym of C. mutabile (Zeder, 1800) by Dubois (1959). The presence or absence of suckers is somewhat in doubt for this species. Kurisu (1932) mentioned a mouth that is 0.35 mm in diameter and a “tubular pharynx” that is 0.375 mm by 0.150 mm; however, the “tubular pharynx” was followed by a “globular pharynx” that was 60 mm by 62 mm. It is likely that the tubular pharynx represents a rudimentary oral sucker.