(Members of ths genus have a prepharyngeal genital pore and the vitelline fields are confluent posteriorly) (Table 21)
Diagnosis. Cyclocoelidae; Ophthalmophaginae. Body, lanceolate to linguiform, sometimes tapered anteriorly. Rudimentary oral sucker absent; rudimentary ventral sucker generally absent. Genital pore prepharyngeal. Ovary posttesticular nearly in line with the tandem or nearly tandem testes often near posterior arch of cyclocoel, but testes may be some distance from ovary (posterior testes half or more distance from ovary to anterior testis in some species; e.g. O. singularis Stossich, 1902 and O. charadrii Yamaguti, 1934). Uterine coils commonly intertesticular overreaching ceca laterally in some species, not invading posttesticular space. Vitelline fields confluent posteriorly. Parasites in infraorbital and nasal sinuses of birds.