Lower slope (500m) to abyssal depths (4000m), in mud.
Original taxon: Lyonsia formosa.
Synonym: aegeensis Sturany.
« Shell oval, equivalve, pearly, thin, and semitransparent. Sculpture: numerous and close-set rows of minute tubercles, arranged lengthwise; the posterior side is also marked with from six to eight diagonal flexuous ribs or folds, of which the innermost is the strongest and forms a keel; there are, besides, traces of other flexuous ribs in the middle and on the anterior side; the posterior side has likewise a few rows of short but irregular prickles as well as the tubercles. Colour silvery-white. Epidermis filmy and only perceptible on the edges of the shell. Margins rounded on the anterior side, gently curved in front, with a slight sinuosity and contraction towards the posterior side, which is somewhat truncated; dorsal margin incurved on each side of the umbo. » – J. G. Jeffreys: “On the Mollusca procured during the ‘Lightning’ and “Porcupine’ expeditions 1868-70” part IV, Proceedings of the Zoological Society of London for the year 1881, London 1882, p.930.
Above and below: 500m deep, Capo Teulada, southwest of Cagliari, S. Sardinia. 24,9mm.
Original pictures provided by A. Nappo (IT).
– CC BY-NC-SA) –
« Beaks triangular, inclined to the anterior side. Ossicle pearly, heart-shaped or notched at the posterior end. Cartilage brownish-yellow, enclosing the ossicle; pit oval, with thickened edges. Hinge-plate long and thick. Inside highly polished and iridescent. Muscular scars broad and distinct. » – Ibid.
The genus is described as follows: « Valves with radial and vertical undulations, gaping behind but not below; siphons very short, with a profusion of long, tentacular filaments and a slender, cylindrical foot. » – W. H. Dall: “Contributions to the Tertiary fauna of Florida”, Transactions of the Wagner Free Institute of Science vol. III part VI, Philadelphia 1903, p.1514.
The genus is described as follows: « Valves with radial and vertical undulations, gaping behind but not below; siphons very short, with a profusion of long, tentacular filaments and a slender, cylindrical foot. » – W. H. Dall: “Contributions to the Tertiary fauna of Florida”, Transactions of the Wagner Free Institute of Science vol. III part VI, Philadelphia 1903, p.1514.
« It is very close to Lyonsia formosa Jeffr. […] and perhaps […] would prove merely a variety of L. formosa. […] The upper edge forms a clear angle with the rear edge by leaking horizontally from the summit and more suddenly bending downwards […] Each shell carries under the umbo a horizontally protruding plate, hollowed out at the top, for receiving the ligament together with the ossiculum. »