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). 

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