Pleurotomariidae, common name the "slit snails", is a family of large marine gastropods in the clade Vetigastropoda. This family is a very ancient lineage; there were numerous species in the geological past. Thegenus includes several hundred fossil forms, mostly Paleozoic. It is one of the oldest gastropod families, commencing in the Cambrian. The superfamily is currently represented by a group of species that live only in deep water. This family has no subfamilies.