A new genus, Dilatatiocauda, is defined to accommodate three new species belonging to the family Porcellidiidae. It is characterised by maxillipeds that do not meet in the mid-line or have a fimbriate process on the basis. Porcellidium dilatatum Hicks, 1971 possesses these features and is moved to the new genus as the type species. Three new species, Dilatatiocauda multidenticulata, D. medialis and D. retroseta from northern New South Wales, Australia are described and placed in the new genus. Three previously described species, Porcellidium tristanense Wiborg, 1964, P. planum Tiemann, 1977 and P. bipartitum Kim & Kim, 1997, although differing in some features, are considered to fall within the parameters of the new genus.