The taxonomic status of the genera Pontigulasia, Lagenodifflugia and Zivkovida (Rhi/opoda: Difflugiidae) Colin G. Ogden Department of Zoology, British Museum (Natural History), Cromwell Road, London SW7 5BD Introduction The significance of the different structural elements utilised to provide an internal dividing wall in the shell of the genus Pontigulasia Rhumbler, 1896 was employed by Ogden (1983) to divide the genus into two, with the creation of a new genus Zivkovida Ogden, 1983. At the same time a new genus Lagenodifflugia was erected by Medioli & Scott (1983) to accommodate Difflugia vas Leidy, 1 874, a species that he (Leidy, 1 879) later redescribed as a variety of Difflugia pyr if ormis. Medioli & Scott (1983) considered their new genus to be distinct from species of Difflugia because the shell was divided into a bulbous main part and a neck, the two parts being separated by an internal diaphragm pierced by a single, central, usually large orifice. In the same work Medioli & Scott redefined the genus Pontigulasia, describing the main characters as a constriction of the neck marking the position where a perforated internal diaphragm often extends across this region, and at times a bent neck combined with the internal restriction simulating a spiral arrangement. They also stated that the diaphragm is seldom present in fossilised forms. The amendment of the diagnosis to contain a 'bent neck' was made to allow Medioli & Scott to include some 'Lecquereusia-like' specimens in their description of Pontigulasia compressa, and to suggest the possibility of combining the genera Lesquereusia and Pontigulasia, the former being the senior synonym. I am most grateful to Dr Drew Haman and Dr Georges Merinfeld for directing my attention to the nomenclature problems posed by the creation of these two new genera. The present report is an attempt to clarify the status and diagnosis of the three genera Pontigulasia, Lagenodifflugia and Zivkovida. Taxonomy The taxonomic problem caused by the creation of two new genera relates to the interpretation and validity of the structures and openings found associated with the inner dividing wall. There are only a few descriptions and figures of these features around which the diagnoses have been erected. One reason for this is the difficulty of trying to see inside the shell either en face or laterally due mainly to the opacity of the mineral particles of which it is constructed. Several techniques have been tried to overcome this, for example immersion in clove oil or Canada balsam and deminerali-sation by hydrofluoric acid. Modern techniques have now obviated this problem and allow a new appraisal of this feature (Ogden, 1983). Each genus will be reassessed here on the basis of the available descriptions and the author's earlier observations. Pontigulasia Rhumbler, 1 896 The first author to recognise the inner dividing wall was Rhumbler (1896) who erected the genus Pontigulasia using this feature as a major diagnostic character to separate it from Difflugia, and described and clearly figured it as an internal 'schlundbriicke'-throat bridge. He described three Bull. Br. Mus. nat. Hist. (Zool.) 52(1): 13-17 Issued 29 January 1987
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