The purpose of this application, under Article 23.9.3 of the Code, is to conserve the widely used generic name StenonasterLambert, 1922 (Echinoidea, Stenonasteridae). The name Stenonaster is threatened by its senior objective synonym Stenocorys Lambert, 1917, that was erroneously considered a junior homonym of StenocorisBurmeister, 1839 (Arthropoda, Hemiptera, Alydidae) and StenocorisRambur, 1839 (= ParomiusFieber, 1861; Arthropoda, Hemiptera, Rhyparochromidae). Strict application of the Code would result in unnecessary confusion since the name Stenonaster has been explicitly used in the geological and palaeontological literature for the last 100 years whereas its senior objective synonym Stenocorys has not been used since it was (erroneously) replaced by Stenonaster. Stenonaster is the type-genus of the family Stenonasteridae, an enigmatic, but important missing link between the two major groups of atelostomate echinoids: Holasteroida and Spatangoida. Reverting the genus name to its senior synonym would necessitate changing the name of this family, which would lead to nomenclatural instability and confusion in the literature. We therefore request a reversal of precedence under the Commission's plenary power, with Stenocorys and Stenocoridae, the senior objective synonyms being suppressed and Stenonaster and Stenonasteridae given precedence.