The measurements of eight populations of Nagelus obscurus (Allen, 1955) are presented and compared with the published data. This increased known limits of the species and lead to proposal of new synonyms: Merlinius camelliae Kheiri, 1972 and Nagelus alpensis Doucet et Luc, 1981 are considered conspecific with N. obscurus. New morphometric data for N. leptus (Allen, 1955) are given and published informations are summarised showing known variation limits for this species.