Mercuria similis

Mercuria similis is a species of small freshwater snail with an operculum, an aquatic gastropod mollusk in the family Hydrobiidae.

This species only tolerates very low salinities, and is perhaps better characterized as a freshwater snail.

Description
The 3–4 mm. high shell is fragile and translucent yellow-white in colour (but often coated with dark deposits). The animal is entirely and uniformly pale and has pale tentacles. Mercuria similis has a proportionately larger body whorl than other hydrobiids.

The shell is short-conical and 3.90–4.50 mm high (Vic-la-Gardiole, Hérault), with a large oval aperture. The penis is long and slim, acute at its distal end, the penial appendix is broad and shorter than the penis which lies on the appendix.

Geographic distribution

 * This species is native to France, Italy, Malta, Algeria, Tunisia and Morocco.
 * Great Britain
 * Ireland
 * Netherlands