Abstract: A new brachypterous, troglophile ground-beetle, Laemostenus (Sphodroides) tiouirii sp. n. (type locality: Ne Tunisia, Jebel Serj Mt., cave of Mine) is described and illustrated. The new species possesses a set of important characters which put it close to/ or within the basal grade of the subgenus, which contains L. aelleni (Antoine), L. foucauldi (De Miré), and L. recticollis (Schaufuss); the new taxon is also closely related to L. alluaudi Bedel. Laemostenus tiouirii sp. n. is however easily recognized from all the above-mentioned species by the combination of four characters: absence of angular protrusion on the anterior margin of male profemor, edentate claws of the onychium, differing shape of the median lobe of aedeagus in lateral aspect, and finer structure of the right paramere. An identification key for the Tunisian species of Sphodroides is provided.