Journal of Conchology Volume 39, Part 4, December 2007

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A new species of Axinus (Bivalvia: Thyasiroidea) from the Baby Bare Seamount, Cascadia Basin, NE Pacific with a description of the anatomy
Oliver, P. G. & Holmes, A. M.

Abstract
A second and new species of living thyasirid is added to the genus Axinus. A. cascadiensis n. sp. was collected from the hydrothermal spring site at Baby Bare Seamount, Cascadia Basin, NE Pacific Ocean at a depth of 2592m. The anatomy is described in detail and compared with the Atlantic species, A. grandis. A. cascadiensis is shown to have highly modified gills that support dense aggregations of bacteriocytes suggesting that this species is highly dependant on the bacterial symbiosis. The mantle is highly modified with a series of partitions and folds that are proposed to function to direct and control the ciliary currents entering and traversing the mantle cavity. The ecological setting is described and thought not to support typical hot vent or cold seep communities due to low levels of sulphides and hydrocarbons. The highly sporadic distribution of both species of Axinus suggests that the genus is localised to small-scale environments, the details of which are not understood. Despite the appearance of fossil Axinus in the Eocene, modern species display the most highly modified anatomy of any extant thyasirid, suggesting that the Thyasiroidea may be much earlier in origin.

Key words: Thyasiroidea, Axinus, new species, functional morphology, hydrothermal springs, deep-sea.

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Another Gloucestershire locality for Lauria sempronii (Charpentier, 1837) (Gastropoda, Stylommatophora, Pupillidae) with observations on the species
Whitehead, P. F.

Abstract
Lauria sempronii (Charpentier, 1837) and intergeneric hybrids were found in the Stroud area of Gloucestershire, England, during 2006.

Key words: Lauria sempronii, Gloucestershire, relict, hybrids, fossil.

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Presence of the Genus Napaeus (Gastropoda: Pulmonata: Enidae) living in all the islands of the Canarian Archipelago: Napaeus lichenicola sp. nov. from Fuerteventura island
Ibáñez, M., Alonso, M. R., Yanes, Y., Castillo, C. & Groh, K.

Abstract
Napaeus lichenicola sp. nov. from Jandía, Fuerteventura Island, is described, the main differences with the nearest species are discussed and data on distribution and conservation status are presented. The functional meaning of the epiphallar caecum and a chambered epiphallar region are inferred for the accommodation, respectively, of the spermatophoral spurlike hook and sharp-pointed denticles.

Key words: Enidae, taxonomy, spermatophore, conservation status, Canary Islands.

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Morphology, biology and systematic position of Epilepton clarkiae (Clark, 1852) (Galeommatoidea: montacutidae) a bivalve commensal with sipunculans
Jespersen, A., Lützen, J. & Oliver, P. G.

Abstract
The shell morphology and anatomy of the micro bivalve Epilepton clarkiae is described from specimens collected in NW Ireland. Anatomical features of a very large subtriangular hypobranchial gland, a pedal protractor bisecting the anterior adductor muscle, a byssus gland divided into symmetrical left and right halves, gills represented by a single demibranch and paired seminal receptacles indicate that the genus Epilepton is most correctly placed in the superfamily Galeommatoidea, and family Montacutidae with closest similarities to the genera Litigiella, Jousseaumiella, and Mioerycina. The genus Potidoma is confirmed to be congeneric with Epilepton. Epilepton clarkiae is a commensal with sipunculans with the specimens examined here associated with Phascolosoma granulatum. The geographic range is from the Mediterranean to southern Scandinavia.

Key words: Epilepton clarkiae, morphology, commensalism, distribution, systematics.

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The distribution of Osilinus lineatus (Monodonta lineata) (da Costa) at its eastern English Channel limit in 2004
Hawthorne, J. B. and Wiffen, L. J.

Abstract
Populations of Osilinus lineatus on Isle of Portland and east Dorset shores have been assessed for the year 2004. The numbers recorded for sites between Portland Harbour and White Nothe indicate a significant increase in population size in recent years. Comparison with populations recorded before the 1963 winter shows that the sparse populations of that time are now represented by only those east of White Nothe. Western Ledges in Portland Harbour support a thriving, apparently breeding, population.

Key words: Osilinus lineatus, distribution, Dorset.

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Taxonomy of Pliocene and Quaternary Thiaridae (Gastropoda) of Israel
Sivan, N., Ben-Ami, F. and Heller, J.

Abstract
This conchometric study explores the taxonomy of both Modern and Plio-Pleistocene Thiaridae of Israel. Modern species include Melanoides tuberculata, today widespread in Africa and Asia and Tarebia granifera, recently introduced via aquarist trade. Fossil species include M. tuberculata, M. dadiana and M. jordanica. M. dadiana differs from M. tuberculata in that it has fewer ribs and in the absence or near absence of tubercles. M. jordanica differs from M. tuberculata in that it has fewer ribs, more conic whorls and a larger aperture. It differs from M. dadiana in its more conic whorls, smaller aperture, shorter body whorl and more ribs.

Key words: Fossil, Levant, Thiaridae, taxonomy.

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Land molluscs of Zanzibar island (Unguja), Tanzania, including a new species of Gulella (Pulmonata: Streptaxidae)
Rowson, B.

Abstract
The land molluscs of Zanzibar island (Unguja), Tanzania are reviewed based on a) published records and b) a quantatitive survey undertaken at Jozani Forest, Unguja in 2000. 58 species are recorded from Unguja, including 16 new records and a new species of Gulella (Pulmonata: Streptaxidae). Two E. African species and one Aldabran species are placed in synonymy. The resulting annotated checklist allows a comparison of the Unguja fauna with that of other parts of E. Africa and more oceanic Indian Ocean islands. Only three additional taxa are yet recorded from the other major Tanzanian coastal islands, Pemba and Mafia. Of the 61 species, seven (11%) are putative endemics for Unguja and/or Pemba/Mafia, 14 (23% show coastal E. African distributions, 24 (39%) show wider E. African distributions, and 16 (26%) show very wide distributions in which anthropogenic introduction has often played a part. 11 (18%) also show affinities with the oceanic Indian Ocean islands; these are briefly discussed. Levels of endemism in Jozani and on Unguja as a whole are comparable to mainland E. African coastal forests that have been subject to similar surveys. Relative to these forests, species richness at Jozani is high (29 species) but variable and skewed towards a few abundant species. Data are provided on a further 25 species recorded from “Zanzibar” but of dubious localisation or identity, as a reference for future work in the region.

Key words: Land molluscs, Tanzania, Zanzibar, Unguja, Gulella tracheia, endemism.

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Recorded natural predation of freshwater pearl mussels Margaritifera margaritifera (l.) in Scotland
Cosgrove, P., Hastie, L. and Sime, I.

Abstract
The endangered freshwater pearl mussel M. margaritifera (L.) has been the subject of much research and the causes for its decline are well known. However, in contrast to other unionids, little or nothing has been published about the natural predators of M. margaritifera. This paper draws together observations of natural predation events from over 300 detailed licensed river surveys in Scotland between 1996 and 2007. M. margaritifera has few known natural predators and the evidence presented suggests that that natural predation does not cause significant mortalities in any of the Scottish rivers surveyed.

Key words: Predators, mortality, Margaritifera margaritifera, mussel populations.

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Incipient parental care in Discus – a plesiomorphic state of a truly endodontid character?
Kuźnik-Kowalska, E. and Pokryszko, B. M.

Abstract
Discus rotundatus (O. F. Müller, 1774), D. ruderatus (Férussac, 1821) and D. perspectivus (Megerle von Mühlfeld, 1818) carry some of their eggs in the umbilicus. We interpret such behaviour as an incipient parental care which has reached its perfection in some Pacific endodontids.

Key words: Land snails, Discus, reproduction, behaviour.

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The endemic Oxychilus species of Marettimo (Aegadian Islands, Italy): O. denatale (Pfeiffer, 1856) (Pulmonata, Zonitidae)
Manganelli, G., Cianfanelli, S. and Giusti, F.

Abstract
The oxychiline zonitid Helix denatale belongs to the genus Oxychilus and is readily distinguished from all other species by its unique combination of shell and anatomy characters (shell discoidal, with many tightly coiled whorls and granulate microsculpture; long vaginal gland; very long epiphallus, very short flagellum, slender penis, extraordinarily thick penial sheath).

Some of these characters are shared with other oxychiline zonitid species: a polygyrate shell with species usually assigned to Oxychilus (Hyalocornea); granulate shell microsculpture with O. oppressus (Shuttleworth, 1878), O. diductus (Westerlund, 1886) and some species of Pseudopolita; slender penis and an extraordinarily thick penial sheath with Oxychilus majori (Paulucci, 1886), but it is not yet possible to state whether they may constitute synapomorphies and support phylogenetic relationships. Consequently, discussion of relationships of O. denatale is postponed to when more data is available, at least on the other Sicilian species.

Key words: Oxychilus denatale, taxonomy, systematics, distribution, Marettimo, Aegadian Islands.

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Short Communication
Abida secale (Draparnaud) in Wales
Alexander, K. N. A. and Harper, J. F.

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