• Abatus (Pseudabatus) nimrodi (Koehler, 1911): planktotrophic
• Abatus agassizii Mortensen, 1910: planktotrophic
• Abatus beatriceae (Larrain, 1986): planktotrophic
• Abatus cavernosus (Philippi, 1845): planktotrophic
• Abatus cordatus (Verrill, 1876): planktotrophic
• Abatus curvidens Mortensen, 1936: planktotrophic
• Abatus ingens Koehler, 1926: planktotrophic
• Abatus kieri McKinney, McNamara & Wiedman, 1988 †: planktotrophic
• Abatus koehleri (Thiéry, 1909): planktotrophic
• Abatus philippii Lovén, 1871: planktotrophic
• Abatus shackletoni Koehler, 1911: planktotrophic
• Abertella aberti (Conrad, 1842) †: planktotrophic
• Abertella cazonesensis (Kew in Dickerson & Kew, 1917) †: planktotrophic
• Abertella dengleri Osborne & Ciampaglio, 2010 †: planktotrophic
• Abertella gualichensis Martínez, Reichler & Mooi, 2005 †: planktotrophic
• Abertella habanensis (Sanchez Roig, 1949) †: planktotrophic
• Abertella kewi Durham, 1957 †: planktotrophic
• Abertella miskellyi Kroh, Mooi, del Rió & Neumann, 2013 †: planktotrophic
• Abertella palmeri Durham, 1957 †: planktotrophic
• Abertella pirabensis (Marchesini Santos, 1958) †: planktotrophic
• Abrekopsis depressispirus (Batten & Stokes, 1986) †: planktotrophic
• Absurdaster hungaricus Kroh, Lukeneder & Gallemí, 2014 †: planktotrophic
• Absurdaster meriani (Ooster, 1865) †: planktotrophic
• Absurdaster puezensis Kroh, Lukeneder & Gallemí, 2014 †: planktotrophic
• Abyssonemertes kajiharai Chernyshev & Polyakova, 2017: planktotrophic
• Acanthechinus dixiei (Cooke, 1941) †: planktotrophic
• Acanthocidaris curvatispinis (Bell, 1892): planktotrophic
• Acanthocidaris hastigera A. Agassiz & H.L. Clark, 1907: planktotrophic
• Acanthocidaris maculicollis (de Meijere, 1904): planktotrophic
• Aceste bellidifera Thomson, 1877: planktotrophic
• Aceste ovata A. Agassiz & H.L. Clark, 1907: planktotrophic
• Aceste weberi Koehler, 1914: planktotrophic
• Achoronemertes scoresbyi (Wheeler, 1934): planktotrophic
• Acriaster sergipensis Smith in Smith & Benggtson, 1991 †: planktotrophic
• Acrocidaris arginensis Weber, 1934 †: planktotrophic
• Acrocidaris borissiaki Weber, 1934 †: planktotrophic
• Acrocidaris cazioti Lambert, 1926 †: planktotrophic
• Acrocidaris crenulata Mercier, 1935 †: planktotrophic
• Acrocidaris marocense Vadet, Marignac, Nicolleau & Reboul, 2007 †: planktotrophic
• Acrocidaris nicolleaui Vadet & Nicolleau, 2000 †: planktotrophic
• Acropeltis atlantica Rey, Taj-Eddine & Witam, 1989 †: planktotrophic
• Acrosalenia arabica Kier, 1972a †: planktotrophic
• Acrosalenia basseae Lambert, 1936 †: planktotrophic
• Acrosalenia bowersi Kier, 1972a †: planktotrophic
• Acrosalenia dhrumaensis Kier, 1972a †: planktotrophic
• Acrosalenia gananensis Stefanini, 1931 †: planktotrophic
• Acrosalenia gauthieri Cotteau, 1879 †: planktotrophic
• Acrosalenia jauberti (Cotteau, 1881) †: planktotrophic
• Acrosalenia marratensis Kier, 1972a †: planktotrophic
• Acrosalenia mathildae Lambert, 1935 †: planktotrophic
• Acrosalenia microstoma Besairie, 1936 †: planktotrophic
• Acrosalenia mideltensis Vadet, Nicolleau & Reboul, 2010 †: planktotrophic
• Acrosalenia pentagona Cotteau, 1879 †: planktotrophic
• Acrosalenia smelliei Currie, 1925 †: planktotrophic
• Acrosalenia somaliensis Currie, 1925 †: planktotrophic
• Acrosalenia spinosa Agassiz, 1840 †: planktotrophic
• Acrosalenia termieri Lambert, 1931 †: planktotrophic
• Acrosalenia wylliei Currie, 1925 †: planktotrophic
• Acrosalenia zararensis Lambert, 1937 †: planktotrophic
• Actapericulum bicarinatum Holmes, 1995 †: planktotrophic
• Acteonemertes bathamae Pantin, 1961: planktotrophic
• Acteonemertes orientalis Hookabe, Fujino, Jimi & Ueshima, 2023: planktotrophic
• Adelopneustes ernsti Smith & Gallemí in Smith, Gallemí, Jeffery, Ernst & Ward, 1999 †: planktotrophic
• Adelopneustes montainvillensis (Sorignet, 1850) †: planktotrophic
• Adenorhagas aurantiafrons Riser, 1990: planktotrophic
• Aegialonemertes chlorophthalma Gibson, 1990: planktotrophic
• Aenigmanemertes norenburgi Sundberg & Gibson, 1995: planktotrophic
• Aeropsis fulva (A. Agassiz, 1898): planktotrophic
• Aeropsis rostrata (Norman, 1876): planktotrophic
• Aetheolineus pulcherrimus Senz, 1993: planktotrophic
• Aetheorhynchus actites Gibson, 1981: planktotrophic
• Africanemertes ruetzleri Kirsteuer, 1965: planktotrophic
• Africanemertes swakopmundi Stiasny-Wijnhoff, 1942: planktotrophic
• Agassizia (Agassizia) powersi Kier, 1972a †: planktotrophic
• Agassizia aequipetala Gregory, 1892 †: planktotrophic
• Agassizia algarbiensis Da Veiga Ferreira, 1962 †: planktotrophic
• Agassizia alveari Sánchez Roig, 1949 †: planktotrophic
• Agassizia avilensis Sánchez Roig, 1949 †: planktotrophic
• Agassizia camagueyana Weisbord, 1934 †: planktotrophic
• Agassizia caobaensis Sánchez Roig, 1953 †: planktotrophic
• Agassizia caribbeana Weisbord, 1934 †: planktotrophic
• Agassizia cyrenaica Desio, 1929 †: planktotrophic
• Agassizia eugeniae Brito & Ramires, 1974 †: planktotrophic
• Agassizia excentrica A. Agassiz, 1869: planktotrophic
• Agassizia flexuosa Sánchez Roig, 1949 †: planktotrophic
• Agassizia guanensis Sánchez Roig, 1951 †: planktotrophic
• Agassizia lamberti Palmer in Sánchez Roig, 1949 †: planktotrophic
• Agassizia pinarensis Sánchez Roig, 1952 †: planktotrophic
• Agassizia regia Israelsky, 1924 †: planktotrophic
• Agassizia scrobiculata Valenciennes, 1846: planktotrophic
• Aguayoaster aguayoi Sánchez Roig, 1952 †: planktotrophic
• Aguayoaster schickleri Donovan & Rowe, 2000 †: planktotrophic
• Akrostomum stannii Grube, 1840: planktotrophic
• Akrostomum valdiviae (Bürger, 1909): planktotrophic
• Alaonemertes michaelseni Stiasny-Wijnhoff, 1942: planktotrophic
• Alaxinus oclairi Gibson, Wickham & Kuris, 1990: planktotrophic
• Albanemertes rovinjensis Senz, 1993: planktotrophic
• Albertechinus devonicus Boczarowski, 2001 †: planktotrophic
• Albertechinus montanus Stearn, 1956 †: planktotrophic
• Algonemertes alba Corrêa, 1954: planktotrophic