Various published hypotheses regarding circumscription and relationships of species within the Radula parvitexta and R. ventricosa species groups were tested using molecular data from three chloroplast markers. The phylogeny resolves five clades within the R. parvitexta species group in Australia, which proves polyphyletic across two subgenera, or three subgenera if R. madagascariensis is included. One clade represents an undescribed species, R. psychosis sp. nov., one corresponds to R. madagascariensis, a new record for Australia, the others to R. ratkowskiana, R. tasmanica and R. robinsonii. R. ratkowskiana is reinstated from synonymy of R. tasmanica, and R. parvitexta is placed into synonymy of R. robinsonii. A second new species belonging to the R. parvitexta species group, R. kilgourii sp. nov., is described; however, it was not included in the phylogeny. Three clades were resolved within the R. ventricosa species group in Australia, which is nested within subg. Metaradula. These clades corresponded to R. jovetiana, R. loriana, which is reinstated from synonymy of R. ventricosa, and two new species, namely, R. myriopoda sp. nov. and R. forficata sp. nov. R. ventricosa is excluded from the Australian flora, because all material is referrable to R. loriana. R. forficata and R. kilgourii had not been collected before the present study. R. myriopoda and R. jovetiana exhibit overlap in morphology of the sterile gametophyte and can be reliably separated only on characters associated with the perianth mouth. They can be considered semicryptic species, and would not have been recognised independent of fieldwork and molecular investigations conducted as part of the present study.