Rissoella diaphana (Alder, 1848)
Norway to British Isles, to Mediterranean, Azores. Absent from the Baltic and most of the North Sea. Grazer in intertidal and infralittoral grounds, often around coralline and red algae. Also present in some brackish-water places, as long as the algae it feeds on can survive there (Barnes & al., 1994).

Original taxon: Rissoa diaphana. Synonym: glabra.
15-25m deep, Málaga, Andalucia, S. Spain, 1mm.
The animal in Forbes & Hanley: A history of British Mollusca and their shells vol. I, London 1853, plate JJ.
 
The genus Jeffreysia was given by J. Alder after this animal, which was the type-species. The operculum, especially, is quite particular, which bears a kind of pillar similar to the spine in some species of Neritidae that use it for some muscular attachment. Alder in Forbes & Hanley: « The animal is pale yellow with three longitudinal bands of rich brown on the body, and blotches of the same colour on the cloak, which, seen through the transparent shell in a fresh state, may readily be mistaken for markings on the latter. »
Specimens from La Franqui, Leucate, Occitania, S. France.
1-1,3mm. Original pictures provided by S. Clanzig (FR).
(CC BY-NC-SA)

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