As nouns the difference between flatworm and turbellarian
is that flatworm is any of very many parasitic or free-living worms, of the phylum platyhelminthes , having a flattened body with no skeleton or body cavity while turbellarian is (biology) any flatworm of the class turbellaria.
As an adjective turbellarian is
characteristic of these creatures.
flatworm
Noun
(
en noun)
Any of very many parasitic or free-living worms, of the phylum Platyhelminthes , having a flattened body with no skeleton or body cavity.