On Arcacythere Hornibrook, 1952 (Cytheracea, Ostracoda, Crustacea), a senior synonym of Rockallia Whatley, Frame & Whittaker, 1978

Abstract. The type specimens of Arcacythere chapmani Hornibrook, 1952 (the type species of Arcacythere Hornibrook, 1953; Tertiary, New Zealand) have been re-examined and are shown to have internal carapace features identical to those of Rockallia Whatley, Frame & Whittaker, 1978. Rockallia is known from Cenozoic deep-sea sediments worldwide and from the Oligocene and Miocene of northwestern Europe. The external carapace morphologies of Arcacythere and Rockallia show only minor distribution of the fossae. Rockallia is, therefore, shown to be a subjective junior synonym of Arcacythere. An emended diagnosis of A. chapmani is given.