Family. Paramphistomidæ, Stiles and Goldberger, emend. 1910.
Sub-family. Cladorchiinæ, Fisch., 1901.
Genus. Watsonius, Stiles and Goldberger, 1910.
Cladorchinæ.—Body pyriform. Ventral pouch absent. Acetabulum ventral or (?) ventro-subterminal, very large, margins projecting, aperture small. Genital pore in front of bifurcation of gut, not surrounded by a sucker; ductus hermaphroditicus apparently absent. Excretory pore at posterior end of excretory vesicle, behind Laurer’s canal. Oral sucker with a pair of irregularly globular suctorial pouches; œsophagus thickened distally; cæca long, not wavy; end in acetabular region.
Male Organs.—Testes two lobed, smaller than acetabulum; longitudinally, nearly or quite coinciding; transversely they abut or slightly overlap; preovarial in equatorial and caudal thirds. Pars musculosa not largely developed; cirrus pouch absent.
Female Organs.—Ovary and shell gland post-testicular. Vitellaria extend from gut fork to slightly beyond gut ending; uterus intercæcal, partly post-testicular. Laurer’s canal in front of excretory vesicle.
Type Species.—Watsonius watsoni, Conyngham, 1904.
Watsonius watsoni, Stiles and Goldberger, 1910.
Syn.: Amphistomum watsoni, Conyngham, 1904; Cladorchis watsoni, Shipley, 1905.