ON THE MORPHOLOGY AND SYSTEMATIC POSITION OF THE FAMILY MEYLIIDAE (NEMATODA, CHROMADORIA)

Meylia alata from the North Sea and Gerlachius lissus from the White S ea, both taxa of the Meyliidae, have several morphological features in common: 1) short pharynx, with nerve ring at the narrow posterior par t, and protruded pharyngeal glands lying free along the intestine; 2) two prominent pseudocoelomocytes in between the cardia and reproductiv e system; 3) absence of rectum and anus; 4) unusual female gonads comb ining antidrom and outstretched ovary types in which oocytes increase successively in size in the direction of the vulva although oogonia is sue from the germinal zone in the direction opposite to the vulva. The meyliid species share the last three characteristics with the genus C yartonema. The pharynx type in the meyliids may be interpreted as a de rivative condition in comparison with the type in Cyartonema. The fami lies Meyliidae De Coninck, 1965 and Cyartonematidae Tchesunov, 1990 ar e considered to be sister taxa from which the Meyliidae is in general more apomorph. Diagnoses are given for the superfamily Meylioidea, and the families Meyliidae and Cyartonematidae.