Hydromedusae observed during night dives in the Gulf Stream Author Schuchert, Peter Muséum d’histoire naturelle, C. P. 6434, CH- 1211 Genève 6, Switzerland peter.schuchert@ville-ge.ch Author Collins, Richard 880 NE 33 rd Street, Boca Raton, Florida, USA rc6684@icloud.com text Revue suisse de Zoologie 2021 2021-10-21 128 2 237 356 journal article 10.35929/RSZ.0049 172fa5c5-c0c4-4bd7-b710-d608237b8458 0035-418 5639938 Genus Turritopsis McCrady, 1857 Synonymy: See Schuchert (2020) . Diagnosis: Medusae with high bell, proximal portion of radial canals swollen through vacuolated gastrodermal cells, forming a peduncle-like mass on top of manubrium, in larger animals continued on manubrium as perradial ribs. Tentacles numerous and evenly distributed. Mouth four-lipped, fringed with numerous spherical nematocyst clusters, these with or without a distinct stalk. Ocelli adaxial on tentacle base. Fig. 10. Larsonia pterophylla . (A) BFLA4453, lateral view of animal, size 27 mm. (B) BFLA4453, close up of manubrium in lateral view. (C) Animal photographed 08-AUG-20181 part of bell margin in aboral view showing rudimentary tentacle bulbs (warts). Polyp stage forming erect, branching colonies, sidebranches and hydranth pedicels adnate for some distance, perisarc tubes not nested. Hydranths spindleto club-shaped; filiform tentacles scattered over much of hydranth body. Gonophores develop on the hydrocauli in perisarc covered region and are liberated as medusae. Remarks: The genera Turritopsis McCrady, 1857 and Oceania Péron & Lesueur, 1810 are morphologically not separable (comp. Schuchert, 2016 ). The purported difference of the stalked oral nematocyst buttons in Oceania is not tenable as also T. nutricula has stalked clusters (see below). However, to avoid unnecessary taxonomic changes, the two genera should not be synonymized until a comprehensive molecular phylogeny using several marker genes confirms this.