Bilamellate form. Holotype NIWA 89736: Subantarctic region of New Zealand, Bounty Platform, NZOI Station A751; 47.743° S, 179.124° E; depth 155 m; 16 Nov. 1962; NIWA 89736 leg.; Agassiz medium trawl. A small piece of the holotype is deposited at the Museum of Evolution in Uppsala, Sweden, UPSZTY 178605.