This key, covering 171 species and subspecies of nematodes in 49 genera, is based on the the listings in the author's "Catalogue of Helminths of Waterfowl" (McDonald, 1969b), but includes 19 additional forms from his continuing survey of new literature.
Additional publication details
Federal Government Series
Key to nematodes reported in waterfowl
Department of the Interior, Bureau of Sport Fisheries and Wildlife