W. wilsoni (Harrah, 1922)

Type host. Common snipe, Gallinago gallinago (Linnaeus) (given as Gallinago wilsoni Seebohm; not a valid species) ( Charadriiformes: Scolopacidae).

Type locality. Creston, Iowa, USA.

Additional host. Western sandpiper, Calidris mauri Cabanis (Syn. Ereunetes mauri Cabanis) ( Charadriiformes: Scolopacidae)— Yamaguti (1971).

Additional locality. Oklahoma, USA—Yamaguti (1971).

Remarks. This species was originally described as Cyclocoelum wilsoni Harrah, 1922 but considered to be a synonym of W. triangulare (Harrah, 1922) by Bashkirova (1950), of Cyclocoelum (H.) tringae Stossich, 1902 (= Neohaematotrephus tringae [Stossich, 1902] n. comb.) by Dubois (1959) and of H. lanceolatum (Wedl, 1858) by Macko & Feige (1960). This species has a pretesticular ovary that forms a triangle with the testes (Haematotrephinae), a postpharyngeal genital pore, the vitelline fields are not confluent posteriorly and the testes are side by side or nearly so, placing it in Wardianum . Rudimentary oral sucker present—Harrah (1922).