The purpose of this application, under Articles 80.7.2 and 81.1 of the Code, is to reinstate as available the generic names Thyone Oken, 1815 and Psolus Oken, 1815, which were introduced by Oken (1815) in a work that was rejected by the Commission in Opinion 417 because it was not consistently binominal. The names acquired availability from subsequent use by Lesson (1830) with concepts that differ completely from Oken's, and from the currently accepted usage of these names. Thyone and Psolus are among the most frequently used generic names in the Holothuroidea. It is requested that the Commission reinstate the availability of the names Thyone Oken, 1815 and Psolus Oken, 1815 published in the rejected work for the sake of nomenclatural stability.