The boreal Atlantic Ocean is characterized by its limited number of Po
lycystine radiolarian species, about 70 in total. The taxonomy and ont
ogeny of all the Actinommida species in these waters are discussed and
the following species illustrated: Actinomma boreale, Actinomma lepto
derma leptoderma (emended), A. leptoderma longispina n. subsp., A. tri
nacria (emended) and Drymyomma elegans. A key to the boreal Atlantic O
cean Actinommida is provided.