The members of this phylum are called as flatworms. 

Unique features of phylum Platyhelminthes: 

1. Body shape: Body of these animals is dorsoventrally flattened. 

2. Coelom: They are acoelomates. 

3. Germ layers: Platyhelminthes are triploblastic. 

4. Body organization: They show organ-system grade of organization.

5. Forms: Most of them are endoparasites and few are free-living. Parasitic forms have hooks and suckers for attachment to the hosts’ body. In parasitic forms, body is covered by cuticle and in free-living forms it is covered by cilia. 

6. Digestive system: Parasitic forms generally lack digestive system. In free-living forms, the digestive system is incomplete. 

7. Body plan: They show blind-sac body plan. 

8. Excretion and osmoregulation: It occurs by flame cells or protonephridia. 

9. Reproduction: They are mostly hermaphrodite (bisexual). Self fertilization is seen. 

10. Few animals show high power of regeneration and show polyembryony. e.g. Planaria, Taenia (Tapeworm), Fasciola (Liver fluke) are included in this phylum.