Acrocirrus Grube and Macrochaeta Grube (Polychaeta Sedentaria), comprising at present 14 species, are removed from the Cirratulidae and placed in a new family. The descriptions of the type species of the genera and of five other species are materially improved. Acrocirrus trisectus and Macrochaeta pege are newly described; Acrocirrus heterochaetus okotensis Imajima is elevated to species rank. Diagnoses and records as well as keys for identification are given for all species of the family.
