Review of Ptycholaimellus Cobb (Nematoda, Chromadoridae), with descriptions of three species

Nematodes of the genus Ptycholaimellus Cobb, 1920 are unique in possessing a collar by which the head is separated from the body. The collar is raised from a groove at the border between the neck and the remainder of the body. The contents of the ventral gland cell are emptied in the groove in at least 9 out of 14 species. It is suggested that the amphids are located in the groove. Fourteen species are considered to belong to Ptycholaimellus . Two Ptycholaimellus species are described as new to science, that is, P. jacobi sp.n. and P. vincxae sp.n.; P. ponticus (Fihpjev, 1922) is redescribed. Ptycholaimellus ponticus sensu Stekhoven (1950) and Boucher (1972) from the Mediterranean off France differs from the other Ptycholaimellus species by its subcuticular ornamentation and shape of spicules, hence these specimens are regarded as belonging to a new species: Ptycholaimellus boucheri sp.n. Chromadorissa inaequibulba Aminova & Galtsova, 1978 is transferred to Ptycholai- mellus as P. inaequibulbus. Ptycholaimellus ponticus from Europe and P pandispiculatus (Hopper, 1961) from the east coast of North America are assumed to have colonized brackish waters independently.