78 Bulletin of Zoological Nomenclature 49( 1 ) March 1 992 OPINION 1664 RissoiDAE Gray, 1847 (Mollusca, Gastropoda): given precedence over TRUNCATELLiDAE Gray, 1840 Ruling (1) Under the plenary powers rissoidae Gray, 1847 and other family-group names based on Rissoa Desmarest, 1814 are hereby given precedence over truncatellidae Gray, 1 840 and other family-group names based on Truncatella Risso, 1 826 whenever their type genera are placed in the same family-group taxon. (2) The name rissoidae Gray, 1847 (type genus Rissoa Desmarest, 1814) is hereby placed on the Official List of Family-Group Names in Zoology, with the endorsement that it and other family-group names based on Rissoa are to be given precedence over TRUNCATELLIDAE Gray, 1840 (type genus Truncatella Risso, 1826) and other family-group names based on Truncatella whenever their type genera are placed in the same family-group taxon. (3) To the entry for truncatellidae Gray, 1840 on the Official List of Family-Group Names in Zoology is hereby added the endorsement that it and other family-group names based on Truncatella Risso, 1826 are not to be given priority over RISSOIDAE Gray, 1847 and other family-group names based on Rissoa Desmarest, 1814 whenever their type genera are placed in the same family-group taxon. (4) The entry for bithyniidae Gray, 1857 on the Official List of Family-Group Names in Zoology is hereby amended to give Troschel ( 1 857) as the author of the name. (5) The name Rissoa Desmarest, 1814, type species by subsequent designation by Bucquoy, Dautzenberg & Dollfus (1884) Rissoa ventricosa Desmarest, 1814, is hereby placed on the Official List of Generic Names in Zoology. (6) The entry for Truncatella Risso, 1826 on the Official List of Generic Names in Zoology is hereby amended to state that its type species by subsequent designation by Lowe (1855) is Truncatella costulata Risso, 1826 (a junior subjective synonym of Helix subcylindrica LinnaQus, 1767). (7) The name ventricosa Desmarest, 1814, as published in the binomen Rissoa ventricosa (specific name of the type species of Rissoa Desmarest, 1814), is hereby placed on the Official List of Specific Names in Zoology. (8) The entry on the Official List of Specific Names in Zoology for subcylindrica. Helix, Linnaeus, 1767 is hereby amended to state that it is the senior subjective synonym of Truncatella costulata Risso, 1 826, the type species of Truncatella Risso, 1826. History of Case 2699 An application for the conservation of the family-group name rissooidea (or rissoacea) Gray, 1847 by giving it precedence over truncatelloidea (or truncatellacea) Gray, 1840 was received from Drs G. Rosenberg & G.M. Davis {Academy of Natural Sciences, Philadelphia, Pennsylvania, U.S.A.) on 28 December 1988. After correspondence the case was published in BZN 47: 104-109 (June 1990). Notice of the case was sent to appropriate journals. In relation to the proposed place-ment of HYDROBiiDAE Troschcl, 1857 on the Official List (proposal (4) on BZN 47: 107),
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