New and little known nematodes from the North Sea

Two new species of free-living marine nematodes from a sublittoral region in the North Sea off the Belgian coast are described: Richtersia deconincki sp.n. and Pomponema coomansi sp.n. Gonionchus villosus Cobb, 1920 is rediscovered and redescribed. Calomicrolaimus monstrosus (Gerlach, 1953) comb.n. is discussed and Microlaimus conspicuous Lorenzen, 1973 is synonymized with it. Females and juveniles of M. annelisae Jensen, 1976 were also found and are discussed; since the holotype of this species is lost, a neotype has been designated.