Ceriantharia (Cnidaria) of the World: an annotated catalogue and key to species Author Stampar, Sergio N. Universidade Estadual Paulista (UNESP), FCL / Assis, Laboratorio de Evolucao e Diversidade Aquatica; LEDA, Departamento de Ciencias Biologicas, Assis, Brazil & Universidade Estadual Paulista (UNESP), Departamento de Zoologia, Instituto de Biociencias, Botucatu, SP, Brazil https://orcid.org/0000-0002-9782-1619 sergiostampar@gmail.com Author Reimer, James D. University of The Ryukyus, Faculty of Science, Department of Biology, Chemistry, and Marine Science, MISE (Molecular Invertebrate Systematics and Ecology) Laboratory, Okinawa, Japan & University of The Ryukyus, Tropical Biosphere Research Center, Okinawa, Japan https://orcid.org/0000-0003-0453-8804 Author Maronna, Maximiliano M. Universidade de Sao Paulo (USP), Instituto de Biociencias, Sao Paulo, SP, Brazil https://orcid.org/0000-0002-2590-639X Author Lopes, Celine S. S. Universidade Estadual Paulista (UNESP), FCL / Assis, Laboratorio de Evolucao e Diversidade Aquatica; LEDA, Departamento de Ciencias Biologicas, Assis, Brazil & Universidade Estadual Paulista (UNESP), Departamento de Zoologia, Instituto de Biociencias, Botucatu, SP, Brazil Author Ceriello, Hellen Universidade Estadual Paulista (UNESP), FCL / Assis, Laboratorio de Evolucao e Diversidade Aquatica; LEDA, Departamento de Ciencias Biologicas, Assis, Brazil & Universidade Estadual Paulista (UNESP), Departamento de Zoologia, Instituto de Biociencias, Botucatu, SP, Brazil https://orcid.org/0000-0003-1199-2773 Author Santos, Thais B. Universidade Estadual Paulista (UNESP), FCL / Assis, Laboratorio de Evolucao e Diversidade Aquatica; LEDA, Departamento de Ciencias Biologicas, Assis, Brazil & University of The Ryukyus, Faculty of Science, Department of Biology, Chemistry, and Marine Science, MISE (Molecular Invertebrate Systematics and Ecology) Laboratory, Okinawa, Japan Author Acuna, Fabian H. Instituto de Investigaciones Marinas y Costeras (Iimyc) CONICET; Facultad De Ciencias Exactas y Naturales Universidad Nacional de Mar Del Plata Funes 3250. 7600 Mar Del Plata, Argentina & Estacion Cientifica Coiba (Coiba-Aip), Clayton, Panama, Republica de Panama Author Morandini, Andre C. Universidade de Sao Paulo (USP), Instituto de Biociencias, Sao Paulo, SP, Brazil & Universidade de Sao Paulo (USP), Centro de Biologia Marinha, Sao Sebastiao, SP, Brazil https://orcid.org/0000-0003-3747-8748 text ZooKeys 2020 952 1 63 http://dx.doi.org/10.3897/zookeys.952.50617 journal article http://dx.doi.org/10.3897/zookeys.952.50617 1313-2970-952-1 961036180C3A4DE9BCC19AE0A824B9D8 4DD4C3F03B1C546FA3471BEC6C4CE3E9 9 Cerianthus bathymetricus Moseley, 1877 Cerianthus bathymetricus Moseley, 1877: 302-305; Andres 1883 : 350; van Beneden 1897 : 142; Pax 1910 : 167; Mello-Leitao 1919 : 37; Molodtsova 2000 : 14-15, 17, 19; Molodtsova 2001b : 913 Type locality. Deep sea, North Atlantic (35° 26'N 50° 53'W), at 5000 m depth. Distribution. Only known from deep water at the type locality. Remarks. This species is one of the smallest tube-dwelling anemone species known. The described specimens are only 2.5 cm long and lived in a very long membranous tube of more than 11 cm in length. The description is not detailed but provides some information on the anatomy, indicating a very long hyposulcus (especially in figure 17, Moseley 1877 ). Molodtsova (2001b) proposed that this species should be placed within the family Arachnactidae , however we are uncertain about this classification as some species of Cerianthidae have comparatively long hyposulcus regions, and the small size of this species may be misleading. Additionally, the description of the tube is much more consistent with the organization of Cerianthidae (see Stampar et al. 2015a ). Thus, we choose to maintain this species as valid until additional studies say otherwise. Type material. Not found in this study, but the original description provided a graphic representation.