Comparison of Myja longicornis Bergh, 1896 with other aeolidacean taxa that have been proposed to have relationships with it (Calma, Tergipes) and which are covered by present analysis [type species of the genus Facelina, F. auriculata (Müller, 1776)]. A–HMyja cf. longicornis from Thailand, living animal ca. 10 mm in length A dorsal view of hydroids in situ B lateral view of hydroids in situ (left), egg mass on the hydroid (right) C details of cerata D smooth masticatory processes of jaws (indicated by arrows), SEM E pharynx, dissected dorsally to show very narrow radula (indicated by an arrow), LM F whole radula, SEM G anteriormost part of radula to show sacoglossan-like small knife-shaped teeth, SEM H teeth from the middle part of radula, SEM; I, J Myja longicornis Bergh, 1896 external view and radula (anterior part), reproduced from the first description by Bergh (1896); K–O Facelina auriculata jaws and radula of a specimen from UK, collected together with neotype K masticatory process (well-defined denticles indicated by arrow), SEM L radula (arrow) on odontophore, to show that anteriormost teeth are not reduced, LM M anterior part of radula to show that teeth are not reduced N anteriormost tooth of radula O two anterior teeth of radula P radula (middle part) of Calma glaucoides (Alder & Hancock, 1854) from Norway Q radula (middle part) Tergipes tergipes (Forsskål in Niebuhr, 1775). Scale bars: 20 μm (D, N, O, Q); 50 μm (F, K); 10 μm (G, P); 5 μm (H); 100 μm (M). Photographs of living specimens by Chanon Ngernthongdee and Siwat Worachananant, SEM images by AV Martynov. Figures I and J are reproduced from Bergh (1896), the publication not currently under copyright.