Trematoda

"Trematoda is a class within the phylum Platyhelminthes," he said.

Trematoda, trem-a-tō′da, n.pl. a class of flat-worms whose members are parasitic in or on a great variety of animals, the body unsegmented, leaf-like or more or less cylindrical, and provided with adhesive suckers.—n.

Most of the Platodaria have not the muscular pharynx, which is very advanced in the Turbellaria and Trematoda.