Hyrrokkin sarcophaga gen. et sp. n., earlier known as Pulvinulina punctulata, is a foraminiferan which infests mainly bivalves, especially Acesta excavata, sponges of the family Geodiidae and the stone corals Lophelia pertusa and Madrepora oculata. It penetrates the body-wall of its host and feeds on its soft tissues. The life cycle is believed to be a normal one with an alternation of generation, a microspheric generation, adapted for planktonic dispersal, and a megalospheric generation. Gamontogamy occurs and the megalospheric generation comprises few individuals which remain settled on the host specimen after the schizogony of a microspheric specimen.