Material of three similar and probably related genera of the viviparous ophidiiform family, Bythitidae, has been studied. The monotypic Hastatobythites is only known from the original two specimens; re-examination of the paratype and information of the holotype clearly demonstrates the validity of the genus. The revision of Saccogaster (Cohen Nielsen 1972) was based on 15 specimens. Since then 29 additional specimens have been collected representing 11 species, three of which are here described: S. brayae, horrida and nikoliviae. Three of the 11 Saccogaster species, S. melanomycter, S. normae and S. rhamphidognatha, differ so much from the remaining eight that a new genus, Parasaccogaster, is described. The main diagnostic characters used for the three genera are: A pair of spines on frontal plate behind eyes, spines on snout, length of gill filaments on anterior arch, number and length of developed gill rakers, size of gill opening, thickness of skin, head pores, otolith morphology, color marks on head, neuromasts on head and head morphometrics, fin ray counts.