Lamellomphalus manusensis new genus, new species is described from a hydrothermal vent site of the Manus Back Arc Basin. The familial assignment is based on morphologies of shell and external anatomy. The new taxon is superficially similar to some members of Peltospiridae McLean, 1989 in general shell shape, but differs from all peltospirids in having sex dimorphism and presence of a copulatory organ. Lamellomphalus manusensis is characterized by possessing haliotiform shell with some degree of coiling, which could be considered as an intermediate form in the family Neomphalidae McLean, 1981, between species with regularly coiled shells (Cyathermia Waren and Bouchet, 1989; Lacunoides Waren and Bouchet, 1989; Planorbidella Waren and Bouchet, 1993, and Solutigyra Waren and Bouchet, 1989) and limpet-like shells (Neomphalus McLean, 1981 and Symmetromphalus McLeah, 1990). This feature thus distinguishes the new taxon from other neomphalids. A phylogenetic reconstruction based on cytochrome c oxidase I gene (COI) also supports its placement within Neomphalidae.