During the last 23 years the identities of three tergipedid aeolids occurring in New Zealand have been questioned. Their identities are re-examined. Local specimens named Cuthona alpha Baba and Hamatani, 1963 are certainly referable to this species, their identity confirmed by the presence of a bristled border to the masticatory process of the jaw and a small stylet at the tip of the penis. Though the local specimens should be renamed C columbiana (O'Donoghue, 1922), the conspecificity of this species with C alpha is rejected because of deficiency in the original description of the former. The similarity between Cuthona rickettsi Behrens, 1984 and C columbiana and C alpha is examined. The identities of the other two species, C scintillans Miller, 1977 and C reflexa Miller, 1977 are confirmed. Cuthona scintillans is shown to be distinctive from five other green coloured Cuthona species, not only by the four characters used previously but also by five others, the colourless or pate yellow transparent body, broadly based tapered rhinophores, long linear cerata, zoned ceratal diverticula colouring and high arched radular teeth. Cuthona reflexa is distinguishable from C. perca (Marcus, 1958), with which it has been synonymised, by the S-shaped cerata, higher number of pre-pericardial ceratal rows, little or no opaque white surface pigment, smoothly arched radular teeth, and straight penial stylet. A fourth species, Cuthona beta (Baba and Abe, 1964) is easily distinguished from the similarly coloured C sibogae (Bergh, 1905). Re-examination of the local Cuthona species led to a re-assessment of several other tergipedid genera based on the arrangement of the digestive ducts. As a result the genus Cuthona Alder and Hancock, 1855 is restricted to one species, C nana (Alder and Hancock, 1842), and the genus Trinchesia von Ihering, 1879 re-introduced for the rest of the species previously included in Cuthona.
