BULLETIN OF ZOOLOGICAL NOMENCLATURE

Recent work on trematode parasites of freshwater fishes has shown that, if the Law of Priority is strictly applied, the species commonly known as Rhipidocotyle illensis (Ziegler, 1883) Vejnar, 1956, must be known as R. polymorphus (Baer, 1827) and the forgotten name Gasterostomum fimbriatum Siebold, 1848 must be applied to the species widely known as Bucephalus polymorphus Baer, 1827. At the same time, the well known generic name Rhipidocotyle Diesing, 1858 must fall as a synonym of Bucephalus Baer, 1827, and the forgotten name Gasterostomum Siebold, 1848 must be revived for the genus known at present as Bucephalus. The Commission is asked to take the necessary steps to prevent these changes being made. In European freshwater fishes there are two common species of trematodes of the family BUCEPHALIDAE, known as Bucephalus polymorphus, Baer, 1827 and Rhipidocotyle illensis (Ziegler, 1883) Vejnar, 1956. It has been SLSsnmtd i\v2^. Bucephalus polymorphus develops from the cercaria described under this name by Baer in 1827, but the cercaria of the trematode now known by that name has not yet been described, although it was figured by Kinkelin(1968). 2. While studying the biology of these two species, both of which occur in Poland, I examined bivalves (the first intermediate host), cyprinid fishes (the second intermediate host) and predatory fishes (the definitive host); I found two different cercariae from which I experimentally obtained metacercariae of two species, but the metacercaria oi Rhipidocotyle illensis developed from cercariae identical with those described hy ^ditr diS Bucephalus polymorphus. Detailed data on the morphology of all developmental stages can be found in Baturo (1977). 3. As a result of this study it has become necessary to set in order the names of these two species of Trematoda. For stability of nomenclature it is necessary to maintain the names commonly used Bull. zool. Nomencl. vol. 36, part 1 , July 1979 Bulletin of Zoological Nomenclature 3 1 and accepted in all keys, textbooks and monographs: the generic name Bucephalus and the specific name B. polymorphus for the species known under this name; the other species, which belongs to the genus Rhipidocotyle Diesing, 1858, should under the Law of Priority be known as R. campanula (Dujardin, 1845). The history of the case is as follows. 4. Baer (1827:570—589) established the genus Bucephalus for the new species B. polymorphus (the type species by monotypy). He based the description on sporocysts and cercariae from the bivalves Anodonta mutabilis Clessin and Unio pictorum Linnaeus. 5. In 1845 Felix Dujardin described from the intestine of Esox lucius Linnaeus small adult trematodes which, according to the author, represent the same species as metacercariae that he had formerly found on the branchia of Cyprinus idus Linnaeus. He classified them in the genus Distoma and gave the new name campanula. The description of the anterior organ given by Dujardin suggests that he was dealing with the adult trematode known today under the name Rhipidocotyle illensis (Ziegler, 1883). 6. Siebold (1848) gave the first short description of the adult trematode from the intestine of Perca fluviatilis Linnaeus and Lucioperca sp. and erected the new genus Gasterostomum for it with the new STpecies fimbria tum. Siebold expressed the assumption that the cercaria described by Baer was a larva of this adult stage. 7.Wagener (1852, 1857, 1858) gave in his works a more accurate description of Gasterostomum fimbriatum, together with drawings of the trematodes. He states that the trematode G. fimbriatum that he found is characterised by five tentacles on the anterior organ. In his next work he presented drawings of the trematode described and said that G. fimbriatum Siebold was probably a synonym oi Bucephalus polymorphus Baer. A year later Wagener considered G. fimbriatum Siebold dind Distoma campanula Dujardin to be synonyms of B. polymorphus. He regarded G. fimbriatum Siebold as a sexually mature, tailless B. polymorphus