This study concludes the series of reviews on European athecate hydroids and anthomedusae, providing updated classifications, descriptions, and illustrations of all species. The present work mainly treats the remaining capitate families, but taxonomic comments and updates on some filiferan taxa are also given.
The genus name Russellia Kramp, 1957 is preoccupied and the new name Heterotentacula n. gen. and the family level name Heterotentaculidae n. fam. is proposed to replace them. Janiopsis Bouillon, 1980 is also a preoccupied genus name. No replacement name is necessary as Janiopsis is regarded as congeneric with Merga Hartlaub, 1914. The frequently used genus name Heterotiara Maas, 1905 is invalid and must be replaced by Protiaropsis Stechow, 1919.
Tubularia ralphi Bale, 1884, Tubularia gracilis von Lendenfeld, 1885, Tubularia australis Stechow, 1924, and Tubularia warreni Ewer, 1953 are all recognized as new synonyms of Ectopleura crocea (L. Agassiz, 1862). Mediterranean records of Ectopleura minerva Mayer, 1900 are here attributed to E. wrighti and E. minerva does not likely occur in European waters. A reexamination of the type material of Corymorpha appelloefi Bonnevie, 1901 made it clear that it must be regarded as synonym of Corymorpha nutans M. Sars, 1835. Meiorhopalon arenicolum Salvin-Plawen, 1987 is recognized as a new synonym of Euphysa aurata Forbes, 1848. Examination of the type material of Coryne filiformis (Rees, 1936) showed that it is inseparable from Coryne pintneri Schneider, 1898. C. filiformis must thus be regarded as a new synonym of C. pintneri. Eugotoea petalina Margulis, 1989 is likewise a new synonym of Rhabdoon singulare Keferstein & Ehlers, 1861.