Geocenamus rugosus (Siddiqi, 1963) Brzeski, 1991

(Table 3 & 4; Figs 3, 5 F–J, 7, 8 G–P)

The results of the present study indicate that G. rugosus is a widespread species in Iran, with 30 populations of this species collected from the rhizosphere of different plants in the country (Table 3). The species comes close to G. quadrifer, G. conicaudatus n. sp., G. s t e g u s (Thorne & Malek, 1968) Brzeski, 1991 and G. lenorus (Brown, 1956) Brzeski, 1991 . For more detailed comparison of G. rugosus and G. quadrifer, readers are encouraged to see Loof (1978) and Mulk (1978). Among the diagnostic characters mentioned in those two studies, tail shape in some individuals of certain populations of G. rugosus from Iran comes close to that of G. quadrifer (Fig. 7 N, O), but other differences are still visible. The two other species, G. s t e g u s and G. lenorus, are very similar to G. rugosus, with some differences in the number of longitudinal striae, head shape and presence/absence of a post-rectal sac.