Alvania discors (Allan, 1818)
Mediterranean, in shallow water down to circalittoral. Its shell is often found near or inside Posidonia meadows. Grazer and detritus feeder. Original taxon: Turbo discors. Many synonyms: crassicostata, discrepans, ferruginosa… Subadult specimen with a strong premature labial thickening, collected at 8m deep, on algae, Livorno, Toscana, W. Italy. 4,7mm.
« Shell pointed, with strong longitudinal ribs and transverse striae ; inside ribbed ; body whorl about equal to the length of the spire. » – T. Allan: “Sketch of the geology of the environs of Nice”, Transactions of the Royal Society of Edinburgh vol. VIII, London 1818. The shape can vary a lot, but two constant features are the dotted pattern on the base, and the double row of white spiral nodules at the periphery of each whorl, just above the suture. – On Posidonia leaves, east of Karyotes, Lefkas island, Ionian archiplegao, W. Greece. 3,7-4mm.
Very thin and weak radial microsculpture. Under stones at 4m deep, NE. of the small venitian fortress, SE. of the citadel, Methóni, Messinia, SW. Peloponnese, SW. Greece. 4,7mm.
An other synonym is sardea Risso, for pale specimens.
8m deep, Bodrum area, Muğla Province, SW. Turkey. 4,5mm.
Dark shell with a smaller protoconch, from 8m deep, Bozcaada island, Çanakkale province, W. Marmara, NW. Turkey. 4,2mm.
2m deep, Uvala Puć, Luka Gornji Molunat, S. Croatia. 5,1mm.
Animal more or less dark, brownish-grey, with yellow dots and lines on the tentacles and the muzzle. 10cm deep, Vlaška Bay, Brač island, Split-Dalmatia Comitat, S. Croatia. 4mm.
Original picture provided by R. Stanić (HR).
– (CC BY-NC-SA) –
A contrasted pair. Left: another 4mm long specimen from Vlaška Bay; right, a pale shell from 3m deep, Sabuša Bay, Molat island, Zadar Comitat, Croatia. 4,6mm. The difference of sizes in the two protos derives from the difference of sizes of the shells. Original pictures provided by R. Stanić (HR).
– (CC BY-NC-SA) –
In discors the protoconch is not spirally striated. In schwartziana it is. This is the reason why the dark Alvania at bottom right is, despite its discors paintings, actually a schwartziana. The colour of the protoconches does not seem to be a meaningful criterion.

0-0,5m deep, Uvala Žorljevica, southern coast of Molat island. The top row shows three discors: 3,9-3,7-4,15mm. Bottom row: a discors (3,8mm) and the schwartziana (3,85mm).

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