A flatworm is in the family of platyheliminthes and has a flat body with bilateral symmetry.
The group includes species that are free-living such as planarians but also internal and external parasites such as flukes and tapeworms. The digestive system of most flatworms is relatively simple. It consists of a mouth, pharynx, and either a simple or branched intestine. Animals Invertebrates. Flatworms are divided into the following taxonomic groups: 1  Planarians and relatives (Turbellaria) - There are about 4,500 species of planarians and their relatives alive today. 2  Members of this group are mainly free-living, nonparasitic flatworms. A planarian is one of many flatworms of the Turbellaria class. It is also the common name for a member of the genus Planaria within the family Planariidae. Sometimes it also refers to the genus Dugesia. Planaria are common to many parts of the world, living in both saltwater and freshwater ponds and rivers. From Wikipedia, the free encyclopedia. The flatworms, or Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning flat and ἕλμινς (root: ἑλμινθ-), helminth- , meaning worm) are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. The remaining Platyhelminthes form a monophyletic group, one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three main groups of more complex bilaterians. There are different types/species of flatworms. A flatworm is in the family of platyheliminthes and has a flat body with bilateral symmetry. They also have soft but solid body … 's. If I'm not mistaken, they are parasitic life forms. Over half of all known flatworm species are parasitic, and some do enormous harm to humans and their livestock. Schistosomiasis, caused by one genus of trematodes, is the second-most devastating of all human diseases caused by parasites, surpassed only by malaria. The remaining Platyhelminthes form a monophyletic group, one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three main groups of more complex bilaterians. 1 Planarians and relatives (Turbellaria) - There are about 4,500 species of planarians and their relatives alive today. 2  Members of this group are mainly free-living, nonparasitic flatworms. 3  Planarians and their relatives have a soft, flat body that is covered with ciliated skin. Animals Invertebrates. Flatworms are divided into the following taxonomic groups: 1  There are different types/species of flatworms. A flatworm is in the family of platyheliminthes and has a flat body with bilateral symmetry. They also have soft but solid body … 's. If I'm not mistaken, they are parasitic life forms.  CLASSIFICATION OF PLATYHELMINTHES. (Girish Chandra). PHYLUM PLATYHELMINTHES. Commonly known as flat worms, they are acoelomate, triploblastic and bilaterally symmetrical animals which have no skeleton, respiratory and circulatory systems. Alimentary canal when present is in blind sac plan. Class TURBELLARIA (Dugesia; Bipalium; Leptoplana; Notoplana). They are free living eddy worms, with flattened body and mouth located on the ventral side. Suckers are absent and epidermal cells are multiciliated. Most flatworms look very similar, though, so Procotyla fluviatilis looks a lot like these pictures. One of the reasons Procotyla fluviatilis is so common is because it is able to live in most bodies of water, including streams, ponds, and lakes. Like most flatworms, they prefer shallow water. All flatworms have a soft body and a triangle-shaped head. They also have eye-spots on top of their heads which can see light. Flatworms are not closely related to most other worms, such as earthworms. Bodies are flat instead of round, and they do not have segments. Phylum Platyhelminthes. The Phylum Platyhelminthes is dominated by the parasitic flukes (Monogenea, 3000 spp. and Trematoda, 8000 spp.) and tapeworms (Cestoda, 5000 spp.). 
http://animals.about.com/od/invertebrates/fl/flatworms.htm https://en.wikipedia.org/wiki/Planarian https://en.wikipedia.org/wiki/Flatworm http://www.answers.com/Q/Classification_of_a_flatworm https://en.wikipedia.org/wiki/Flatworm http://animals.about.com/od/invertebrates/fl/flatworms.htm http://www.answers.com/Q/What_is_the_taxonomy_of_a_flatworm http://www.iaszoology.com/platyhelminthes-classification/ http://www.fcps.edu/islandcreekes/ecology/flatworm.htm http://winvertebrates.uwsp.edu/Platyhelminthes.html
what is the classification of flatworms