Haliactis arctica is a poorly known species of sea anemone of the family Halcampactinidae known only from the Arctic. So far, there have been no reports of it after the original description, based on a few specimens from Greenland, Spitsbergen, the Barents Sea, Novaya Zemlya and the Chukchi Sea. The rich collection of the Zoological Institute RAS, which includes more than 100 specimens, has allowed a detailed morpho-anatomical study of this sea anemone. Examination of the external and internal morphology of H. arctica indicates a noticeable variability of structural features, especially the retractor muscles, parietal muscles and acontia. Comparison of characters between H. arctica with the other representatives of Halcampactinidae shows significant differences in the organization of these anemones. Their morphological differences and also significant geographic remoteness suggest that they should be attributed to different families, however, at present it is impossible to conduct thorough molecular genetic studies that can confirm or refute this assumption.
