Barnacles (Cirripedia: Thoracica) taken in the Clarion-Clipperton region, central Pacific, during cruises of the Research VesselYuzhmorgeologia (2003, 2006, 2007, 2010, 2011) were studied. Three species, Amigdoscalpellum torbenwolffi Zevina, 1981,Arcoscalpellum radiatum Rao et Newman, 1972 and Catherinum tortilum (Zevina, 1973), were collected in five samples from depths of 4680–4877m. The data obtained considerably extend the previously known distributions of these three species.
With 7 Text-figures SYNOPSIS The deep-sea barnacles Pachylasma and Hexelasma are little known and a few species have been sporadically recorded from isolated localities of all oceans. Of the genus Pachylasma, only two species P. crinoidophilum PrLSBRY and P.japonicum HrRo have been known from Japan. A third species P. scutistriatum BROCH is newly added to the Japanese fauna. The other known species, P. ecaudatum HrRo formerly referred to Pachylasma, is now transferred to the genus Hexelasma, of which two species H. velutinum HoEK and H. callistoderma PILSBRY only have been so far known from Japan. An attempt to subdivide the family Chthamalidae into three subfamilies (Catophragminae, Chthamalinae and Pachylasminae) is newly presented. Syste~natic Account of the Japanese Species (Revised) Genus Pachylasma DARWIN, 1854 Diagnosis. Chthamalidae having a wall of eight compartments, in which the rostrum and rostrolaterals are united by inconspicuous, linear sutures, or are wholly con-crescent in the adult stage, the wall thus becoming virtually six-plated. Radii wanting or very narrow and not well differentiated from the parietes. Wall-plates non-porous, not ribbed on the inner surface in adults. Basis essentially membranous but often secondarily calcified in adults. Scutum without an adductor ridge and a pit for lateral depressor muscle. Caudal appendages present. Labrum without a median notch. Mandible with three teeth and a pectinated lower angle. Living in deep-sea. Type species. Pachylasma giganteum (PHILIPPI, 1836) (Original designation by DARWIN, 1854) 1)
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