Members of the Phylum Platyhelminthes are typically called flatworms because of their flattened bodies. These animals lack appendages, and their bodies can take many forms, such as slender, leaflike, or ribbon-like. This diverse group of bilateral invertebrates ranges widely in size from 1mm or less to tapeworms that grow to many meters in length. There are both free-living and parasitic flatworms, and species are found in both freshwater and marine environments.