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''Onchnesoma'' is one of the two genera that constitute the family Phascolionidae of Phylum Sipuncula, described by Koren and Danielssen established in 1873 as the type species to ''Onchnesoma steenstrupii''.〔Stephen, A. C., and. Edmonds S. J. (1972): The Phyla Sipuncula and Echiura. vii+528 Trustees of The British Museum of Natural History. London. ISBN 0-565-00717-3〕〔Ditadi, A.S.F. & Migotto, A.E. (1982): O Filo Sipuncula. Concelho Nacional de Desemvolvimento Cientifico e Tecnologico CNPq Brasilia. 43p.〕〔Cutler, Edward B. & Cutler, Norma J (1985): A revision of the genera ''Phascolion'' Théel and ''Onchnesoma'' Koren and Danielssen (Sipuncula). Proceedings of Biological Society of Washington 94(4):809-850〕〔Cutler, Edward B. & Gibbs, Peter E. (1985): A Phylogenetic analysis of higher taxa in the Phylum Sipuncula. Systematic Zoology 34(2):162-173.〕〔 Cutler, Edward B. (1994): The Sipuncula: their systematic, biology and evolution. Comstock Publishing Associates of Cornell University. Ithaca, New York. 406p ISBN 0-8014-2843-2 (Google Book )〕 ==Description== The species of this genus are usually small in size (with a trunk of less than 1 cm in length). The introverted is much longer than the trunk. The body wall muscle layers presents continuous. The disc may present oral tentacles (usually less than 10 and about 8 mm. in length) arranged around the mouth, but those tentacles can be reduced in size or completely absent. The retractor muscle system is a highly modified introverted form fused to form a muscle retractor. The anus is located in the distal half of introverted. Gallbladder contractile is rarely observed and if present is without villi. They have a single nephridium.〔Cutler, Edward B. (1973): Sipuncula of the Western North Atlantic. Bulletin of American Museum of Natural History, 152(3):103-203.〕〔〔Gibbs, Peter E and Cutler, Edward B. (1987): A classification of the phylum Sipuncula. Bulletin of the British Museum (Natural History) Zoology, 52(1):43-58〕〔 ==Species== * ''Onchnesoma intermedium'' Murina, 1976〔Murina, V.V. (1976): New and rare species of sipunculida from the East China Sea. Vestnik Zoologi, 2:62-67〕〔〔 * ''Onchnesoma magnibathum'' Cutler, 1969〔Cutler, Edward B. (1969): New species of Sipuncula from western North Atlantic. Proceedings of Biological Society of Washington, 82:209-218.〕 〔〔〔Smithsonian National Museum of Natural History. Antarctic Invertebrates: Onchnesoma magnibathum Cutler, 1969 http://invertebrates.si.edu/antiz/taxon_view.cfm?ScreenWidth=1003&ScreenHeight=567&taxon=8585&MODE=taxon〕 * ''Onchnesoma squamatum'' (Koren y Danielssen, 1875)〔Koren, J. and Danielssen, D.C. (1875): Bidrag de norskr Gephyreens Naturhistorie. Nytt. Magasin for Naturvidenskapene, 21:201-138.〕〔〔 * ''Onchnesoma steenstrupii'' Koren y Danielssen, 1875〔〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Onchnesoma」の詳細全文を読む スポンサード リンク
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