Unidentia sandramillenae sp. n. A holotype ZMMU Op-617, live, dorsal view , 7 mm in length (fixed) B same, details of cerata C uncollected specimen, lateral view D same, among athecate hydroids, possible prey E holotype, jaws, lateral view, SEM F G details of masticatory processes of jaw H posterior rows of radula, SEM I anterior rows of radula J egg mass K scheme of reproductive system L penis with hollow stylet, light microscopy. Abbreviations: am ampulla fgm female gland mass go genital opening hd hermaphoroditic duct p penis pr prostate ps penial sheath vd vas deferens rsp proximal receptaculum seminis Scale bars: E = 200 μm; F =10 μm; G = 5 μm; H, I = 20 μm; K = 0.5 mm. Photos of living specimens and eggs by B. Picton, other photos and SEM images by A.V. Martynov, drawings by T.A. Korshunova.