The Phylum Nematoda (or Nemata), the roundworms, are small (1-2 mm). They are filiform in shape and unsegmented. They are not taken to lower taxanomic level by OEPA.
The Phylum Nematomorpha, the horsehair worms, contains two families, the Gordidae (Gordius sp.) and the Parachordodidae (Paracordius sp.).