Alder J. & Hancock A. (1845-1855). A monograph of the British nudibranchiate Mollusca: with figures of all the species. The Ray Society, London. Published in 8 parts:Part 7 Fam.1 Plate 27 *Idalia elegans Leuckart, 1828 synonym Okenia elegans (Leuckart, 1828) accepted name Idalia leachii Alder & Hancock, 1854 synonym Okenia leachii (Alder & Hancock, 1854) accepted name