Nemathelminthes Gegenbaur, 1859 see Phylum Nematoda Gegenbaur, 1859 Class Nematoda Gegenbaur, 1859 Subclass Torquentia Order Monhysterida Filipjev, 1929 Suborder Monhysterina De Coninck & Schuurmans Stekhoven, 1933 Family Xyalidae Chitwood, 1951