Six specimens representing a new genus of cyclocoelid, Psophiatrema greineri n. gen., n. sp. (Digenea: Cyclocoelidae: Cyclocoelinae), were collected from the air sacs of a common or grey-winged trumpeter, Psophia crepitans (Gruiformes: Psophiidae), from Guyana on 19 January 2001. The bird was being maintained in an aviary at Emerald Forest Bird Gardens, Fallbrook, California. The new genus has an intertesticular ovary forming a triangle with the testes, placing it in Cyclocoelinae. There are currently 2 genera recognized in Cyclocoelinae: Cyclocoelum and Selfcoelum. The new genus is most similar to Selfcoelum by having a postpharyngeal genital pore, but differs from both Cyclocoelum and Selfcoelum by having the vitelline fields confluent posteriorly. A revised key to the Cyclocoelinae is provided to include the new genus, and the subfamily diagnosis is emended to reflect that the vitelline fields can be either confluent or not posteriorly.