[On the genus Nematodirus Ransom 1907 (Nematoda: Trichostrongyloidea)].

N. roscidus Railliet, 1911, from Dama dama (Italy); N. abnormalis May, 1920, from Ovis aries, Capra hircus and Rupicapra rupicapra (France, Italy, Australia); N. lanceolatus Ault, 1944, from Ovis aries (Iran); N. europaeus Jansen, 1972, from Capreolus caperolus and Ovis musimon (first record) (France); N. davtiani alpinus Biocca, Balbo & Costantini, 1974, from Rupicapra rupicapra (Italy); N. rupicaprae Biocca, Balbo & Costantini, 1983, from Rupicapra rupicapra (France); N. ibicis Biocca, Balbo & Costantini, 1983, from Capra ibex (Italy). In addition four new species are described: N. Bioccai n. sp. from Ovis aries (Iran), resembles N. lamae Becklund, 1963 from Lama pacos and Vicugna vicugna (Peru), N. ibicis Biocca, Balbo & Costantini, 1983 from Capra ibex (Italy), and N. archari Sokolova, 1948 from Ovis ammon (USSR), in that ray 8 is long and closely adpressed to ray 6 throughout most of its length. The new species differs from the first of the above in the form of the point of the spicules and from the remaining two since the two branches of the dorsal ray are well separated and the dorsal lobe well differentiated from the rest of the bursa. N. chabaudi n. sp. from Rupicapra rupicapra (France) is similar to N. oiratianus Rajewskaja, 1929, from Cervus canadensis asiaticus and Ovis aries (USSR), and N. europaeus Jansen, 1972 from Capreolus capreolus (Holland), in the disposition of its bursal rays. Il is distinguished mainly by the presence of three tubercles on the tail of the female. N. hugonnetae n. sp., from Rupicapra rupicapra (France), resembles N. bioccai n. sp. in the general form of the bursa and in that the spicules are fused at their extremities, but is distinguished by the form of the point of the spicules and by the disposition of the bursal bosses. N. iranicus n. sp. from Ovis aries (Iran), resembles N. hugonnetae n. sp. in the disposition of the bursal rays but is distinguished by having more cuticular ridges and a shorter ray 8. On the basis of morphology, host distribution and host paleogeography, an hypothesis is given on the evolution of the Nematodirus and the Nematodirinae. According to this hypothesis Nematodirus arose in North American Camelidae from an ancestor similar to lamanema (which occurs in neotropical Camelidae), later passed to nearctic Odocoileinae and Caprinae, and was transported secondarily into the palaearctic region with its hosts. Beginning with this genus, the Nematodirinae evolved in holarctic ruminants (Nematodirella), holarctic Leporidae (Nematodiroides and Rauschia) and palaearctic and oriental Ochotonidae (Murielus).