CŒLOM-dwelling trematodes are very rare. The only monogenetic form ever found in the cœlom of a vertebrate is Dictyocotyle cœliaca Nybelin, 1941. A solitary specimen was found at Goteborg on April 1, 1940, attached to the surface of the liver in a ray (Raja lintea Fries) caught the previous day near Skagen. At first sight the trematode was mistaken for the well-known cloacal parasite Calicotyle kroyeri, but closer inspection revealed several distinctive characters, notably the irregular arrangement of numerous shallow loculi on the posterior disk (opisthaptor), which was devoid of hooks, the reticular nature of the testes and the five finger-like terminations of the filiform ovary1. In contrast, the opisthaptor of Calicotyle has one central loculus and seven peripheral loculi and bears one pair of hooks with recurved points, the testes are diffuse and follicular and the ovary terminates in a single lobe.